build-aux/compute-symver-floor: Fix handling of spaces in CFLAGS
build-aux/compute-symver-floor: Fix handling of spaces in CFLAGS

If you pass CFLAGS with a leading space, " " gets passed to popen and convinces
gcc to try and open a file called " ". This results in a confusing error message
like:

x86_64-pokysdk-linux-gcc: error: : No such file or directory

Avoid this by stripping empty elements out of CFLAGS.

Signed-off-by: Richard Purdie <3b7a1db6efedd40440bc6443bf377195011524e5@linuxfoundation.org>

besser82/libxcrypt,besser82/libxcrypt,besser82/libxcrypt,besser82/libxcrypt