buildsys: drop manual TARGET_SUBARCH .config lookup
buildsys: drop manual TARGET_SUBARCH .config lookup

We source the .config file, so there should be no need to manually extract
it.  If the sourcing doesn't work, then a lot of things break in this file.

Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

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