gcc-testsuite: Fix ppc cpu specification

After this change in qemu:

c7e89de132

there is no 'max' cpu model on ppc. Drop it to clean up ppc gcc testsuite failures.

In order for this to work we do need to pull in the alternative cpu option from
QEMU_EXTRAOPTIONS on powerpc.

(From OE-Core rev: ea3143b243bb979f9b89f01fc2e7826cac0a7d75)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit c447f2b21b20fb2b1829d540af2cc0bf8242700c)
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-devtools/gcc/gcc-testsuite.inc

@@ -51,9 +51,10 @@ python check_prepare() {
         # enable all valid instructions, since the test suite itself does not
         # limit itself to the target cpu options.
         #   - valid for x86*, powerpc, arm, arm64
-        if qemu_binary.lstrip("qemu-") in ["x86_64", "i386", "ppc", "arm", "aarch64"]:
+        if qemu_binary.lstrip("qemu-") in ["x86_64", "i386", "arm", "aarch64"]:
             args += ["-cpu", "max"]
-
+        elif qemu_binary.lstrip("qemu-") in ["ppc"]:
+            args += d.getVar("QEMU_EXTRAOPTIONS_%s" % d.getVar('PACKAGE_ARCH')).split()
         sysroot = d.getVar("RECIPE_SYSROOT")
         args += ["-L", sysroot]
         # lib paths are static here instead of using $libdir since this is used by a -cross recipe