Make private build variables private

Given the convention that the OC_* build varialbes are reserved for
the build system, it seems better to make sure all of them are defined
in the private Makefile.build_config file, rather than in Makefile.config
which gets installed and thus becomes public.

This commit moves the definitions of OC_CFLAGS, OC_CPPFLAGS,
OC_LDFLAGS, OC_DLL_LDFLAGS and OC_EXE_LDFLAGS from Makefile.config.in to
Makefile.build_config.in. It also moves the defintion of MKEXE_VIA_CC,
since this variable relies on private build varables and does not seem
relevant or useful outside of the context of the build of the compiler itself.

Makefile.build_config.in

@@ -50,6 +50,20 @@ INSTALL_OCAMLNAT = @install_ocamlnat@
 DEP_CC=@DEP_CC@ -MM
 COMPUTE_DEPS=@compute_deps@
 
+# Build-system flags to use to compile C files
+OC_CFLAGS=@oc_cflags@
+OC_CPPFLAGS=-I$(ROOTDIR)/runtime @oc_cppflags@
+
+# Additional link-time options
+# To support dynamic loading of shared libraries (they need to look at
+# our own symbols):
+OC_LDFLAGS=@oc_ldflags@
+OC_DLL_LDFLAGS=@oc_dll_ldflags@
+OC_EXE_LDFLAGS=@oc_exe_ldflags@
+
+MKEXE_VIA_CC=\
+  $(CC) $(OC_EXE_LDFLAGS) $(OC_CFLAGS) $(CFLAGS) @mkexe_via_cc_ldflags@
+
 # Which tool to use to display differences between files
 DIFF=@DIFF@
 # Which flags to pass to the diff tool

Makefile.config.in

@@ -78,13 +78,6 @@ CC=@CC@
 CC_HAS_DEBUG_PREFIX_MAP=@cc_has_debug_prefix_map@
 AS_HAS_DEBUG_PREFIX_MAP=@as_has_debug_prefix_map@
 
-### Additional link-time options
-# To support dynamic loading of shared libraries (they need to look at
-# our own symbols):
-OC_LDFLAGS=@oc_ldflags@
-OC_DLL_LDFLAGS=@oc_dll_ldflags@
-OC_EXE_LDFLAGS=@oc_exe_ldflags@
-
 LDFLAGS?=@LDFLAGS@
 
 ### How to invoke the C preprocessor through the C compiler
@@ -175,9 +168,7 @@ OTHERLIBRARIES=@otherlibraries@
 UNIX_OR_WIN32=@unix_or_win32@
 INSTALL_SOURCE_ARTIFACTS=@install_source_artifacts@
 
-OC_CFLAGS=@oc_cflags@
 CFLAGS=@CFLAGS@
-OC_CPPFLAGS=-I$(ROOTDIR)/runtime @oc_cppflags@
 CPPFLAGS=@CPPFLAGS@
 OCAMLC_CFLAGS=@ocamlc_cflags@
 
@@ -214,8 +205,6 @@ MKEXE=@mkexe@
 MKDLL=@mkdll@
 MKMAINDLL=@mkmaindll@
 MKEXEDEBUGFLAG=@mkexedebugflag@
-MKEXE_VIA_CC=\
-  $(CC) $(OC_EXE_LDFLAGS) $(OC_CFLAGS) $(CFLAGS) @mkexe_via_cc_ldflags@
 
 RUNTIMED=@debug_runtime@
 INSTRUMENTED_RUNTIME=@instrumented_runtime@