glsl/build: Build glcpp via the glsl Makefile

Removing the subdirectory recursion provides a small speed up.

Tested-by: Andreas Boll <andreas.boll.dev@gmail.com>
diff --git a/Makefile.am b/Makefile.am
index ee73333..c6fc062 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -53,9 +53,9 @@
 	bin/ltmain.sh					\
 	bin/missing					\
 	bin/ylwrap					\
-	src/glsl/glsl_parser.cc				\
+	src/glsl/glsl_parser.cpp			\
 	src/glsl/glsl_parser.h				\
-	src/glsl/glsl_lexer.cc				\
+	src/glsl/glsl_lexer.cpp				\
 	src/glsl/glcpp/glcpp-lex.c			\
 	src/glsl/glcpp/glcpp-parse.c			\
 	src/glsl/glcpp/glcpp-parse.h			\
@@ -76,8 +76,7 @@
 
 
 parsers: configure
-	$(MAKE) -C src/glsl glsl_parser.cc glsl_parser.h glsl_lexer.cc
-	$(MAKE) -C src/glsl/glcpp glcpp-lex.c glcpp-parse.c glcpp-parse.h
+	$(MAKE) -C src/glsl glsl_parser.cpp glsl_parser.h glsl_lexer.cpp glcpp/glcpp-lex.c glcpp/glcpp-parse.c glcpp/glcpp-parse.h
 	$(MAKE) -C src/mesa/program lex.yy.c program_parse.tab.c program_parse.tab.h
 
 # Everything for new a Mesa release: