package/gcc: fix powerpc toolchain issues with 64-bit capable cores

Some of the powerpc CPUs supported by Buildroot are dual mode CPUs,
which means 32 Bit and 64 Bit mode is supported, and for any 64-bit
capable CPU, GCC defaults to using 64-bit, even if the toolchain tuple
starts with powerpc-* (and not powerpc64-*). This causes issues when
building toolchains with uClibc or musl.

In order to resolve this, we force GCC to understand we want to
generate 32-bit code, using the --with-cpu-32 option.

See here the gcc documentation for details about --with-cpu-32:
https://gcc.gnu.org/install/configure.html

See here for a discussion on the musl mailinglist about the error:
https://inbox.vuxu.org/musl/20220722162900.GB1320090@port70.net/

Fixes:
 - http://autobuild.buildroot.net/results/450/4509d8cfb7d99beb4ef023f170490def1d90f92c
 - http://autobuild.buildroot.net/results/654/6545a464d49f9f3c6740a5208cfad7f09ec4cb8b
 - http://autobuild.buildroot.net/results/cf8/cf866d5320b069eb1e8b4f05e8e58de0ad2ec7b5

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/gcc/gcc.mk

@@ -225,9 +225,17 @@ endif
 ifneq ($(GCC_TARGET_FP32_MODE),)
 HOST_GCC_COMMON_CONF_OPTS += --with-fp-32="$(GCC_TARGET_FP32_MODE)"
 endif
+
+# musl/uClibc-ng does not work with biarch powerpc toolchains, we
+# need to configure gcc explicitely for 32 Bit for CPU's supporting
+# 64 Bit and 32 Bit
 ifneq ($(GCC_TARGET_CPU),)
+ifeq ($(BR2_powerpc),y)
+HOST_GCC_COMMON_CONF_OPTS += --with-cpu-32=$(GCC_TARGET_CPU)
+else
 HOST_GCC_COMMON_CONF_OPTS += --with-cpu=$(GCC_TARGET_CPU)
 endif
+endif
 
 ifneq ($(GCC_TARGET_FPU),)
 HOST_GCC_COMMON_CONF_OPTS += --with-fpu=$(GCC_TARGET_FPU)