guix: use gcc tool wrappers

This way, correct `--plugin` argument are passed through.

This is a prerequisite for LTO (see #25391).

Author: fanquake

contrib/guix/libexec/build.sh

@@ -188,9 +188,9 @@ make -C depends --jobs="$JOBS" HOST="$HOST" \
                                    ${SDK_PATH+SDK_PATH="$SDK_PATH"} \
                                    x86_64_linux_CC=x86_64-linux-gnu-gcc \
                                    x86_64_linux_CXX=x86_64-linux-gnu-g++ \
-                                   x86_64_linux_AR=x86_64-linux-gnu-ar \
-                                   x86_64_linux_RANLIB=x86_64-linux-gnu-ranlib \
-                                   x86_64_linux_NM=x86_64-linux-gnu-nm \
+                                   x86_64_linux_AR=x86_64-linux-gnu-gcc-ar \
+                                   x86_64_linux_RANLIB=x86_64-linux-gnu-gcc-ranlib \
+                                   x86_64_linux_NM=x86_64-linux-gnu-gcc-nm \
                                    x86_64_linux_STRIP=x86_64-linux-gnu-strip \
                                    FORCE_USE_SYSTEM_CLANG=1