guix: build-system: meson: Don't error on unsupported targets.issue-70985

Rather than raising generic errors.

* guix/build-system/meson.scm (make-machine-alist): Return #f if the triplet
is unsupported.
(lower): Return #f if the machine alist is #f.

Change-Id: If6a1f8d1c2073e43107406ac186aa9c845005a95

1 files changed, 62 insertions, 53 deletions

diff --git a/guix/build-system/meson.scm b/guix/build-system/meson.scm
index bf9ca15ecc..b321417773 100644
--- a/guix/build-system/meson.scm
+++ b/guix/build-system/meson.scm
@@ -46,39 +46,46 @@
   "Make an association list describing what should go into
 the ‘host_machine’ section of the cross file when cross-compiling
 for TRIPLET."
-  `((system . ,(cond ((target-hurd? triplet) "gnu")
-                     ((target-linux? triplet) "linux")
-                     ((target-mingw? triplet) "windows")
-                     ((target-avr? triplet) "none")
-                     (#t (error "meson: unknown operating system"))))
-    (cpu_family . ,(cond ((target-x86-32? triplet) "x86")
+  (let ((system
+         (cond
+          ((target-hurd? triplet) "gnu")
+          ((target-linux? triplet) "linux")
+          ((target-mingw? triplet) "windows")
+          ((target-avr? triplet) "none")
+          (else #f)))
+        (cpu-family
+         (cond ((target-x86-32? triplet) "x86")
+               ((target-x86-64? triplet) "x86_64")
+               ((target-arm32? triplet) "arm")
+               ((target-aarch64? triplet) "aarch64")
+               ((target-avr? triplet) "avr")
+               ((target-mips64el? triplet) "mips64")
+               ((target-powerpc? triplet)
+                (if (target-64bit? triplet)
+                    "ppc64"
+                    "ppc"))
+               ((target-riscv64? triplet) "riscv64")
+               (else #f))))
+    (and system
+         cpu-family
+         `((system . ,system)
+           (cpu_family . ,cpu-family)
+           (cpu . ,(cond ((target-x86-32? triplet) ; i386, ..., i686
+                          (substring triplet 0 4))
                          ((target-x86-64? triplet) "x86_64")
-                         ((target-arm32? triplet) "arm")
-                         ((target-aarch64? triplet) "aarch64")
+                         ((target-aarch64? triplet) "armv8-a")
+                         ((target-arm32? triplet) "armv7")
                          ((target-avr? triplet) "avr")
-                         ((target-mips64el? triplet) "mips64")
-                         ((target-powerpc? triplet)
-                          (if (target-64bit? triplet)
-                              "ppc64"
-                              "ppc"))
-                         ((target-riscv64? triplet) "riscv64")
-                         (#t (error "meson: unknown architecture"))))
-    (cpu . ,(cond ((target-x86-32? triplet) ; i386, ..., i686
-                   (substring triplet 0 4))
-                  ((target-x86-64? triplet) "x86_64")
-                  ((target-aarch64? triplet) "armv8-a")
-                  ((target-arm32? triplet) "armv7")
-                  ((target-avr? triplet) "avr")
-                  ;; According to #mesonbuild on OFTC, there does not appear
-                  ;; to be an official-ish list of CPU types recognised by
-                  ;; Meson, the "cpu" field is not used by Meson itself and
-                  ;; most software doesn't look at this field, except perhaps
-                  ;; for selecting optimisations, so set it to something
-                  ;; arbitrary.
-                  (#t "strawberries")))
-    (endian . ,(if (target-little-endian? triplet)
-                   "little"
-                   "big"))))
+                         ;; According to #mesonbuild on OFTC, there does not appear
+                         ;; to be an official-ish list of CPU types recognised by
+                         ;; Meson, the "cpu" field is not used by Meson itself and
+                         ;; most software doesn't look at this field, except perhaps
+                         ;; for selecting optimisations, so set it to something
+                         ;; arbitrary.
+                         (#t "strawberries")))
+           (endian . ,(if (target-little-endian? triplet)
+                          "little"
+                          "big"))))))
 
 (define (make-binaries-alist triplet)
   "Make an associatoin list describing what should go into
@@ -146,29 +153,31 @@ TRIPLET."
             '()
             '(#:target))))
 
-  (bag
-    (name name)
-    (system system) (target target)
-    (build-inputs `(("meson" ,meson)
-                    ("ninja" ,ninja)
-                    ,@native-inputs
-                    ,@(if target '() inputs)
-                    ;; Keep the standard inputs of 'gnu-build-system'.
-                    ,@(if target
-                          (standard-cross-packages target 'host)
+  (and
+   (make-machine-alist target)
+   (bag
+     (name name)
+     (system system) (target target)
+     (build-inputs `(("meson" ,meson)
+                     ("ninja" ,ninja)
+                     ,@native-inputs
+                     ,@(if target '() inputs)
+                     ;; Keep the standard inputs of 'gnu-build-system'.
+                     ,@(if target
+                           (standard-cross-packages target 'host)
+                           '())
+                     ,@(standard-packages)))
+     (host-inputs `(,@(if source
+                          `(("source" ,source))
                           '())
-                    ,@(standard-packages)))
-    (host-inputs `(,@(if source
-                         `(("source" ,source))
-                         '())
-                   ,@(if target inputs '())))
-    ;; Keep the standard inputs of 'gnu-buid-system'.
-    (target-inputs (if target
-                       (standard-cross-packages target 'target)
-                       '()))
-    (outputs outputs)
-    (build (if target meson-cross-build meson-build))
-    (arguments (strip-keyword-arguments private-keywords arguments))))
+                    ,@(if target inputs '())))
+     ;; Keep the standard inputs of 'gnu-buid-system'.
+     (target-inputs (if target
+                        (standard-cross-packages target 'target)
+                        '()))
+     (outputs outputs)
+     (build (if target meson-cross-build meson-build))
+     (arguments (strip-keyword-arguments private-keywords arguments)))))
 
 (define* (meson-build name inputs
                       #:key