build/glsl: fix location of generated files.

Like in src/mesa, use GLSL_BUILDDIR/GLSL_SRCDIR to unambiguously
distinguish between in-tree and generated files.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Christopher James Halse Rogers <christopher.halse.rogers@canonical.com>

src/glsl/Makefile.am

 # builtin_compiler is built before libglsl to generate builtin_function.cpp for libglsl.
 # For this to work, a dummy version of builtin_function.cpp, builtin_stubs.cpp, is used.
 
-# Hack to make some of the non-automake variables work.
-TOP=$(top_builddir)
-
 AM_CFLAGS = \
 	-I$(top_srcdir)/include \
 	-I$(top_srcdir)/src/mapi \
 
 AM_LFLAGS = --nounistd -o$(LEX_OUTPUT_ROOT).c
 
-GLSL_SRCDIR=$(top_srcdir)/src/glsl
 include Makefile.sources
 
 noinst_LTLIBRARIES = libglslcommon.la libglsl.la

src/glsl/Makefile.sources

 # shared source lists for Makefile, SConscript, and Android.mk
 
-GLSL_SRCDIR ?= .
+GLSL_SRCDIR = $(top_srcdir)/src/glsl
+GLSL_BUILDDIR = $(top_builddir)/src/glsl
 
 # libglcpp
 
 	$(GLSL_SRCDIR)/glcpp/pp.c
 
 LIBGLCPP_GENERATED_FILES = \
-	$(GLSL_SRCDIR)/glcpp/glcpp-lex.c \
-	$(GLSL_SRCDIR)/glcpp/glcpp-parse.c
+	$(GLSL_BUILDDIR)/glcpp/glcpp-lex.c \
+	$(GLSL_BUILDDIR)/glcpp/glcpp-parse.c
 
 # libglsl
 
 	$(GLSL_SRCDIR)/builtin_stubs.cpp
 
 BUILTIN_COMPILER_GENERATED_CXX_FILES = \
-	$(GLSL_SRCDIR)/glsl_lexer.cc \
-	$(GLSL_SRCDIR)/glsl_parser.cc
+	$(GLSL_BUILDDIR)/glsl_lexer.cc \
+	$(GLSL_BUILDDIR)/glsl_parser.cc
 
 # libglsl generated sources
 LIBGLSL_GENERATED_CXX_FILES = \
-	$(GLSL_SRCDIR)/$(BUILTIN_COMPILER_GENERATED_CXX_FILES) \
-	$(GLSL_SRCDIR)/builtin_function.cpp
+	$(BUILTIN_COMPILER_GENERATED_CXX_FILES) \
+	$(GLSL_BUILDDIR)/builtin_function.cpp

src/glsl/glcpp/Makefile.am

 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 # IN THE SOFTWARE.
 
-# Hack to make some of the non-automake variables work.
-TOP=$(top_builddir)
-
-GLSL_SRCDIR=$(top_srcdir)/src/glsl
 include ../Makefile.sources
 
 AM_CFLAGS = \