buildsys: fix handling of CFLAG_-W{a,l} vars
buildsys: fix handling of CFLAG_-W{a,l} vars

Need a little indirection/delayed evaluation to handle variables with
equal signs and commas in them.

Reported-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>
Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

majek/uclibc-vx32,atgreen/uClibc-moxie,kraj/uclibc-ng,hwoarang/uClibc,skristiansson/uClibc-or1k,brgl/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,mephi42/uClibc,ndmsystems/uClibc,wbx-github/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,ddcc/klee-uclibc-0.9.33.2,kraj/uclibc-ng,wbx-github/uclibc-ng,waweber/uclibc-clang,ffainelli/uClibc,majek/uclibc-vx32,czankel/xtensa-uclibc,atgreen/uClibc-moxie,hjl-tools/uClibc,mephi42/uClibc,foss-xtensa/uClibc,foss-xtensa/uClibc,brgl/uclibc-ng,hjl-tools/uClibc,hwoarang/uClibc,groundwater/uClibc,atgreen/uClibc-moxie,ddcc/klee-uclibc-0.9.33.2,hjl-tools/uClibc,czankel/xtensa-uclibc,czankel/xtensa-uclibc,kraj/uClibc,waweber/uclibc-clang,hjl-tools/uClibc,foss-xtensa/uClibc,wbx-github/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,ddcc/klee-uclibc-0.9.33.2,ndmsystems/uClibc,brgl/uclibc-ng,foss-xtensa/uClibc,mephi42/uClibc,majek/uclibc-vx32,groundwater/uClibc,hwoarang/uClibc,groundwater/uClibc,skristiansson/uClibc-or1k,hwoarang/uClibc,ndmsystems/uClibc,czankel/xtensa-uclibc,atgreen/uClibc-moxie,mephi42/uClibc,waweber/uclibc-clang,kraj/uClibc,ffainelli/uClibc,ffainelli/uClibc,ndmsystems/uClibc,ddcc/klee-uclibc-0.9.33.2,ffainelli/uClibc,kraj/uclibc-ng,kraj/uClibc,groundwater/uClibc,ffainelli/uClibc,hjl-tools/uClibc,majek/uclibc-vx32,groundwater/uClibc,skristiansson/uClibc-or1k,kraj/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,brgl/uclibc-ng,waweber/uclibc-clang,foss-for-synopsys-dwc-arc-processors/uClibc,skristiansson/uClibc-or1k