[bug#41074] [PATCH] gnu: qemu-minimal: Only build for the host's architecture.

[Efraim Flashner <efraim@flashner.co.il>]

* gnu/packages/virtualization.scm (qemu-minimal)[arguments]: Adjust
configure-flags so that each architecture only builds for its native
architectures.
[synopsis]: Adjust to clarify it's only for the host's architecture.
---

I tested this with building grub and a vm-image and both seem to have
worked without any regressions.

---
 gnu/packages/virtualization.scm | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/gnu/packages/virtualization.scm b/gnu/packages/virtualization.scm
index b9ac18820f..e5d678e685 100644
--- a/gnu/packages/virtualization.scm
+++ b/gnu/packages/virtualization.scm
@@ -1,7 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015, 2016, 2017, 2018 Mark H Weaver <mhw@netris.org>
-;;; Copyright © 2016, 2017, 2018. 2019 Efraim Flashner <efraim@flashner.co.il>
+;;; Copyright © 2016, 2017, 2018. 2019, 2020 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2016, 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2017 Alex Vong <alexvong1995@gmail.com>
 ;;; Copyright © 2017 Andy Patterson <ajpatter@uwaterloo.ca>
@@ -99,7 +99,8 @@
   #:use-module ((guix licenses) #:prefix license:)
   #:use-module (guix packages)
   #:use-module (guix utils)
-  #:use-module (srfi srfi-1))
+  #:use-module (srfi srfi-1)
+  #:use-module (ice-9 match))
 
 (define (qemu-patch commit file-name sha256)
   "Return an origin for COMMIT."
@@ -274,15 +275,33 @@ server and embedded PowerPC, and S390 guests.")
     (supported-systems (delete "mips64el-linux" %supported-systems))))
 
 (define-public qemu-minimal
-  ;; QEMU without GUI support.
+  ;; QEMU without GUI support, only supporting the host's architecture
   (package (inherit qemu)
     (name "qemu-minimal")
-    (synopsis "Machine emulator and virtualizer (without GUI)")
+    (synopsis
+     "Machine emulator and virtualizer (without GUI) for the host architecture")
     (arguments
      (substitute-keyword-arguments (package-arguments qemu)
        ((#:configure-flags _ '(list))
-        ;; Restrict to the targets supported by Guix.
-        ''("--target-list=i386-softmmu,x86_64-softmmu,mips64el-softmmu,arm-softmmu,aarch64-softmmu"))))
+        ;; Restrict to the host's architecture.
+        `(,@(match (or (%current-system)
+                       (%current-target-system))
+             ("x86-64-linux"
+              ''("--target-list=i386-softmmu,x86_64-softmmu"))
+             ("i686-linux"
+              ''("--target-list=i386-softmmu"))
+             ("mips64el-linux"
+              ''("--target-list=mips64el-softmmu"))
+             ("aarch64-linux"
+              ''("--target-list=arm-softmmu,aarch64-softmmu"))
+             ("armhf-linux"
+              ''("--target-list=arm-softmmu"))
+             ((or "powerpc64-linux" "powerpc64le-linux")
+              ''("--target-list=ppc-softmmu,ppc64-softmmu"))
+             ("powerpc-linux"
+              ''("--target-list=ppc-softmmu"))
+             (_ ; An empty list actually builds all the targets.
+              ''()))))))
 
     ;; Remove dependencies on optional libraries, notably GUI libraries.
     (native-inputs (fold alist-delete (package-native-inputs qemu)
-- 
2.26.2