Move CC/CXX saving to a safe place

AC_CHECK_LIB, AC_CHECK_HEADER etc tend to touch CC, so better
move saving of that var to an earlier part of configure

configure.in

@@ -1313,6 +1313,9 @@ if test "$EUID" -eq "0"  -a "z`uname -o 2>/dev/null`" = "zCygwin" ; then
    AC_MSG_ERROR([You must build LibreOffice as a normal user - not using an administrative account])
 fi
 
+save_CC=$CC
+save_CXX=$CXX
+
 AC_PROG_EGREP
 AC_PROG_AWK
 AC_PATH_PROG( AWK, $AWK)
@@ -1877,9 +1880,6 @@ fi
 AC_MSG_RESULT($GCC_HOME)
 AC_SUBST(GCC_HOME)
 
-save_CC=$CC
-save_CXX=$CXX
-
 if test "$GCC_HOME_SET" = "true" ; then
    if test -z "$CC"; then
       CC="$GCC_HOME/bin/gcc"