perf: Use gcc as default compiler

Since its being build from kernel sources which are procecced with
gcc by default KERNEL_CC is gcc, its a constant battle to keep this
compiling with clang, so unless clang is also used to compile kernel
this is a fruitless excercise to use clang just for perf.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

conf/nonclangable.conf

@@ -642,3 +642,4 @@ LDFLAGS:remove:pn-bluez5:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURE
 LDFLAGS:append:pn-bluez5:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'ld-is-lld', ' -fuse-ld=bfd', '', d)}"
 
 LD:pn-gnu-efi:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'ld-is-lld', '${HOST_PREFIX}ld.bfd${TOOLCHAIN_OPTIONS} ${HOST_LD_ARCH}', '${HOST_PREFIX}ld${TOOLCHAIN_OPTIONS} ${HOST_LD_ARCH}', d)}"
+TOOLCHAIN:pn-perf = "gcc"