glsl/linker: Don't include interface name for built-in blocks
glsl/linker: Don't include interface name for built-in blocks

Commit 11096ec introduced a regression in some piglit tests (e.g.,
arb_program_interface_query-resource-query).  I did not notice this
regression because other (unrelated) problems caused failed assertions
in those same tests on my system... so they crashed before getting to
the new failure.

v2: Use is_gl_identifier.  Suggested by Tim.

Signed-off-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Timothy Arceri <5dd83789ef3714029244367ba1ca09f1d7627408@collabora.com>
Cc: 59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler