Fix Archlinux PKGBUILD check() run on ARM

The check() run started to fail after #2288 since ENVTEST_ARCH was not
set correctly on ARM/ARM64. This should fix the problem for the flux-go
and flux-scm AUR packages.

Signed-off-by: Aurel Canciu <aurelcanciu@gmail.com>

.github/aur/flux-scm/PKGBUILD.template

@@ -38,6 +38,14 @@ build() {
 
 check() {
   cd "flux2"
+  case $CARCH in
+    aarch64)
+      export ENVTEST_ARCH=arm64
+      ;;
+    armv6h|armv7h)
+      export ENVTEST_ARCH=arm
+      ;;
+  esac
   make test
 }