caps: Build with gcc

caps relies on GCC vector extensions that clang does not support, and
on the register storage class, which C++17 removed, so build it with
gcc when clang is the default toolchain.

AI-Generated: Uses Claude Code
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-multimedia/recipes-multimedia/caps/caps_0.9.26.bb

@@ -16,6 +16,9 @@ EXTRA_OEMAKE = " \
     CFLAGS='${CFLAGS} -ffast-math -funroll-loops -fPIC -DPIC' \
     ARCH='' \
 "
+# Relies on GCC vector extensions and the register keyword
+TOOLCHAIN = "gcc"
+
 do_compile() {
     oe_runmake all
 }