configure.ac: Add support to enable read-only text segment on x86.
configure.ac: Add support to enable read-only text segment on x86.

Cc: "10.6 11.0" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Bugzilla: https://bugs.gentoo.org/240956
Reviewed-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler