selftests/sgx: Treat CC as one argument

CC can have multiple sub-strings like "ccache gcc". For check_cc.sh,
CC needs to be treated like one argument. Put double quotes around it to
make CC one string and hence one argument.

Fixes: 2adcba79 ("selftests/x86: Add a selftest for SGX")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20220214184109.3739179-3-usama.anjum@collabora.com