libpthread: linuxthreads.old: Allow building for no-legacy-syscalls ABI
libpthread: linuxthreads.old: Allow building for no-legacy-syscalls ABI

Since NPTL port to an ARCH can be non-trivial, we must allow the legacy
pthread lib to be built for the common-generic syscall ABI

Note that only linuxthreads.old is allowed, since "newer" linuxthreads
relies on sysctl which the ABI no longer provides.

Signed-off-by: Vineet Gupta <af669d95a4c0de051445d4cafdbb2c5c4a2838be@synopsys.com>
Cc: Markos Chandras <5cdbcb0e11d2b5ebc39222958c54a1c6329d0c9d@imgtec.com>
Signed-off-by: Bernhard Reutner-Fischer <ce1ac9e9ad16abccd7821f371ad381197b4768ac@gmail.com>

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