getconf: only use specs that are available
getconf: only use specs that are available

On older glibc (like 2.7), the _SC_V7_* symbols are not defined,
making the build of current uClibc fail on Debian Lenny systems and
other systems using a fairly old glibc. So we make sure to only use
the specs names that are defined by the host C library.

Signed-off-by: Thomas Petazzoni <a5d87d2bd7c424ee5cbdb4e978635bf653d5a005@free-electrons.com>
Signed-off-by: Bernhard Reutner-Fischer <ce1ac9e9ad16abccd7821f371ad381197b4768ac@gmail.com>

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