fix parallel build with headers once and for all (i hope)
fix parallel build with headers once and for all (i hope)

groundwater/uClibc,klee/klee-uclibc,atgreen/uClibc-moxie,groundwater/uClibc,wbx-github/uclibc-ng,m-labs/uclibc-lm32,ChickenRunjyd/klee-uclibc,gittup/uClibc,gittup/uClibc,ysat0/uClibc,m-labs/uclibc-lm32,groundwater/uClibc,OpenInkpot-archive/iplinux-uclibc,wbx-github/uclibc-ng,hjl-tools/uClibc,hjl-tools/uClibc,czankel/xtensa-uclibc,ddcc/klee-uclibc-0.9.33.2,atgreen/uClibc-moxie,ysat0/uClibc,czankel/xtensa-uclibc,ddcc/klee-uclibc-0.9.33.2,kraj/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,skristiansson/uClibc-or1k,kraj/uclibc-ng,wbx-github/uclibc-ng,kraj/uClibc,foss-xtensa/uClibc,OpenInkpot-archive/iplinux-uclibc,ddcc/klee-uclibc-0.9.33.2,majek/uclibc-vx32,skristiansson/uClibc-or1k,ffainelli/uClibc,ddcc/klee-uclibc-0.9.33.2,kraj/uClibc,brgl/uclibc-ng,klee/klee-uclibc,hwoarang/uClibc,ffainelli/uClibc,majek/uclibc-vx32,hwoarang/uClibc,skristiansson/uClibc-or1k,groundwater/uClibc,brgl/uclibc-ng,waweber/uclibc-clang,OpenInkpot-archive/iplinux-uclibc,ffainelli/uClibc,gittup/uClibc,waweber/uclibc-clang,klee/klee-uclibc,m-labs/uclibc-lm32,ndmsystems/uClibc,hjl-tools/uClibc,czankel/xtensa-uclibc,foss-xtensa/uClibc,ffainelli/uClibc,waweber/uclibc-clang,foss-xtensa/uClibc,wbx-github/uclibc-ng,OpenInkpot-archive/iplinux-uclibc,mephi42/uClibc,hjl-tools/uClibc,czankel/xtensa-uclibc,mephi42/uClibc,ffainelli/uClibc,ChickenRunjyd/klee-uclibc,kraj/uClibc,gittup/uClibc,ndmsystems/uClibc,hjl-tools/uClibc,ysat0/uClibc,hwoarang/uClibc,klee/klee-uclibc,groundwater/uClibc,ndmsystems/uClibc,kraj/uclibc-ng,mephi42/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,kraj/uClibc,hwoarang/uClibc,majek/uclibc-vx32,atgreen/uClibc-moxie,skristiansson/uClibc-or1k,ysat0/uClibc,ndmsystems/uClibc,foss-xtensa/uClibc,ChickenRunjyd/klee-uclibc,mephi42/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,kraj/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,majek/uclibc-vx32,waweber/uclibc-clang,atgreen/uClibc-moxie,ChickenRunjyd/klee-uclibc,brgl/uclibc-ng,m-labs/uclibc-lm32,brgl/uclibc-ng