build: Set AM_C* instead of CFLAGS/CPPFLAGS

Makefile.am

@@ -30,6 +30,8 @@ AM_CPPFLAGS = -DLIBRARYBUILD \
 	-I$(top_srcdir)/src/libnurbs/internals \
 	-I$(top_srcdir)/src/libnurbs/interface \
 	-I$(top_srcdir)/src/libnurbs/nurbtess
+AM_CFLAGS = $(GL_CFLAGS) $(WARNCFLAGS)
+AM_CXXFLAGS = $(GL_CFLAGS) $(WARNCXXFLAGS)
 
 GLU_LIBRARY_VERSION=1:3:1
 lib_LTLIBRARIES = libGLU.la
@@ -123,6 +125,5 @@ libGLU_la_SOURCES =						\
 	src/libnurbs/nurbtess/sampleMonoPoly.cc			\
 	src/libnurbs/nurbtess/sampledLine.cc			\
 	src/libnurbs/nurbtess/searchTree.cc
-libGLU_la_CFLAGS = $(GL_CFLAGS)
 libGLU_la_LIBADD = $(GL_LIBS)
 libGLU_la_LDFLAGS = -version-number $(GLU_LIBRARY_VERSION) -no-undefined -export-symbols-regex '^glu'

configure.ac

@@ -61,14 +61,19 @@ PKG_CHECK_MODULES(GL, [gl], [], [
 
 dnl Set up C warning flags.
 if test "x$GCC" = xyes; then
-    CFLAGS="$CFLAGS -Wall"
-    CXXFLAGS="$CXXFLAGS -Wall"
+    WARNCFLAGS="-Wall"
+    if test "x$GXX" = xyes; then
+        WARNCXXFLAGS="-Wall"
+    fi
 else
     AC_CHECK_DECL([__SUNPRO_C], [SUNCC="yes"], [SUNCC="no"])
     if test "x$SUNCC" = "xyes"; then
-        WARNFLAGS="-v"
+        WARNCFLAGS="-v"
+        WARNCXXFLAGS="-v"
     fi
 fi
+AC_SUBST([WARNCFLAGS])
+AC_SUBST([WARNCXXFLAGS])
 
 AC_OUTPUT([
     Makefile