Fix cross-compilation

Fetched httpd-2.4.x-cross_compile.diff from upstream bugtracker:
https://issues.apache.org/bugzilla/show_bug.cgi?id=51257#c6

which is a bundle of upstream revisions:
    http://svn.apache.org/viewvc?view=revision&revision=1327907
    http://svn.apache.org/viewvc?view=revision&revision=1328390
    http://svn.apache.org/viewvc?view=revision&revision=1328714

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>

--- a/server/Makefile.in
+++ b/server/Makefile.in
@@ -24,9 +24,14 @@ TARGETS = delete-exports $(LTLIBRARY_NAM
 include $(top_builddir)/build/rules.mk
 include $(top_srcdir)/build/library.mk
 
+ifdef CC_FOR_BUILD
+gen_test_char: gen_test_char.c
+	$(CC_FOR_BUILD) $(CFLAGS_FOR_BUILD) -DCROSS_COMPILE -o $@ $<
+else
 gen_test_char_OBJECTS = gen_test_char.lo
 gen_test_char: $(gen_test_char_OBJECTS)
 	$(LINK) $(EXTRA_LDFLAGS) $(gen_test_char_OBJECTS) $(EXTRA_LIBS)
+endif
 
 test_char.h: gen_test_char
 	./gen_test_char > test_char.h
--- a/configure.in
+++ b/configure.in
@@ -206,6 +206,14 @@ AC_PROG_CPP
 dnl Try to get c99 support for variadic macros
 ifdef([AC_PROG_CC_C99], [AC_PROG_CC_C99])
 
+dnl In case of cross compilation we set CC_FOR_BUILD to cc unless
+dnl we got already CC_FOR_BUILD from environment.
+if test "x${build_alias}" != "x${host_alias}"; then
+  if test "x${CC_FOR_BUILD}" = "x"; then
+    CC_FOR_BUILD=cc
+  fi
+fi
+
 if test "x${cache_file}" = "x/dev/null"; then
   # Likewise, ensure that CC and CPP are passed through to the pcre
   # configure script iff caching is disabled (the autoconf 2.5x default).
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -55,6 +55,8 @@ AC_DEFUN([APACHE_GEN_CONFIG_VARS],[
   APACHE_SUBST(CPPFLAGS)
   APACHE_SUBST(CFLAGS)
   APACHE_SUBST(CXXFLAGS)
+  APACHE_SUBST(CC_FOR_BUILD)
+  APACHE_SUBST(CFLAGS_FOR_BUILD)
   APACHE_SUBST(LTFLAGS)
   APACHE_SUBST(LDFLAGS)
   APACHE_SUBST(LT_LDFLAGS)