CLANGPLUGIN_CPPFLAGS for building plugin for Clang in nonstandard location

(i.e., configure with CLANGPLUGIN_CPPFLAGS=-I.../clang-installation/include
-I.../clang-build/tools/clang/include)

Change-Id: Ic6d2973629103f71c32f44ebba2ac70d137d18e7

compilerplugins/Makefile-clang.mk

@@ -56,7 +56,7 @@ CLANGOBJS=
 define clangbuildsrc
 $(3): $(2) $(SRCDIR)/compilerplugins/Makefile-clang.mk $(CLANGOUTDIR)/clang-timestamp
 	@echo [build CXX] $(subst $(SRCDIR)/,,$(2))
-	$(CXX) $(CLANGCXXFLAGS) $(CLANGDEFS) $(CLANGINCLUDES) -DSRCDIR=$(SRCDIR) $(2) -fPIC -c -o $(3) -MMD -MT $(3) -MP -MF $(CLANGOUTDIR)/$(1).d
+	$(CXX) $(CLANGPLUGIN_CPPFLAGS) $(CLANGCXXFLAGS) $(CLANGDEFS) $(CLANGINCLUDES) -DSRCDIR=$(SRCDIR) $(2) -fPIC -c -o $(3) -MMD -MT $(3) -MP -MF $(CLANGOUTDIR)/$(1).d
 
 -include $(CLANGOUTDIR)/$(1).d
 

config_host.mk.in

@@ -59,6 +59,7 @@ ifneq ($(strip @CFLAGS@),)
 export CFLAGS=@CFLAGS@
 endif
 export CHECK_PARALLELISM=@CHECK_PARALLELISM@
+export CLANGPLUGIN_CPPFLAGS=@CLANGPLUGIN_CPPFLAGS@
 export CLASSPATH=@CLASSPATH@
 export CLUCENE_CFLAGS=@CLUCENE_CFLAGS@
 export CLUCENE_LIBS=@CLUCENE_LIBS@

configure.ac

@@ -5102,7 +5102,7 @@ if test "$COM_GCC_IS_CLANG" = "TRUE"; then
     if test "$compiler_plugins" != "no"; then
         AC_LANG_PUSH([C++])
         save_CPPFLAGS=$CPPFLAGS
-        CPPFLAGS="$CPPFLAGS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS"
+        CPPFLAGS="$CPPFLAGS $CLANGPLUGIN_CPPFLAGS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS"
         AC_CHECK_HEADER(clang/AST/RecursiveASTVisitor.h,
             [COMPILER_PLUGINS=TRUE],
             [
@@ -5122,6 +5122,7 @@ else
     fi
 fi
 AC_SUBST(COMPILER_PLUGINS)
+AC_SUBST(CLANGPLUGIN_CPPFLAGS)
 
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