gcc-configure/gcc-common: Move preconfigure definition to common include

gcc-configure/gcc-common: Move preconfigure definition to common include

There is a race where:

NOTE: recipe libgcc-initial-4.9.1-r0: task do_configure: Started
NOTE: recipe gcc-runtime-4.9.1-r0: task do_preconfigure: Started

| checking build system type... /home/pokybuild/yocto-autobuilder/yocto-worker/nightly-deb/build/build/tmp/work-shared/gcc-4.9.1-r0/gcc-4.9.1/libgcc/../config.sub: line 1711: syntax error near unexpected token `;;'
| /home/pokybuild/yocto-autobuilder/yocto-worker/nightly-deb/build/build/tmp/work-shared/gcc-4.9.1-r0/gcc-4.9.1/libgcc/../config.sub: line 1711: `		;;'
| configure: error: /bin/bash /home/pokybuild/yocto-autobuilder/yocto-worker/nightly-deb/build/build/tmp/work-shared/gcc-4.9.1-r0/gcc-4.9.1/libgcc/../config.sub x86_64-linux failed
| WARNING: exit code 2 from a shell command.

so we need to make sure the preconfigure task executes in all shared
work contexts.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Ross Burton <ross.burton@intel.com>