Add an optional separate install prefix for internal components. rdar://10217046

Some files installed by clang are not relevant for general users and we'd like
to be able to install them to a different location.  This adds a new
--with-internal-prefix configure option and a corresponding PROJ_internal_prefix
makefile variable, which defaults to the standard prefix.  A tool makefile
can specify that it should be installed to this internal prefix by defining
INTERNAL_TOOL.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145234 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/configure b/configure
index c2c3f4c..bf63d49 100755
--- a/configure
+++ b/configure
@@ -711,6 +711,7 @@
 EXTRA_LD_OPTIONS
 CLANG_SRC_ROOT
 BINUTILS_INCDIR
+INTERNAL_PREFIX
 NM
 ifGNUmake
 LN_S
@@ -1451,6 +1452,7 @@
                           plugin-api.h file for gold plugin.
   --with-bug-report-url   Specify the URL where bug reports should be
                           submitted (default=http://llvm.org/bugs/)
+  --with-internal-prefix  Installation directory for internal files
   --with-tclinclude       directory where tcl headers are
   --with-udis86=<path>    Use udis86 external x86 disassembler library
   --with-oprofile=<prefix>
@@ -5671,6 +5673,17 @@
 
 
 
+# Check whether --with-internal-prefix was given.
+if test "${with_internal_prefix+set}" = set; then
+  withval=$with_internal_prefix;
+else
+  withval=""
+fi
+
+INTERNAL_PREFIX=$withval
+
+
+
 { echo "$as_me:$LINENO: checking for BSD-compatible nm" >&5
 echo $ECHO_N "checking for BSD-compatible nm... $ECHO_C" >&6; }
 if test "${lt_cv_path_NM+set}" = set; then
@@ -10476,7 +10489,7 @@
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 10479 "configure"
+#line 10492 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -21937,6 +21950,7 @@
 EXTRA_LD_OPTIONS!$EXTRA_LD_OPTIONS$ac_delim
 CLANG_SRC_ROOT!$CLANG_SRC_ROOT$ac_delim
 BINUTILS_INCDIR!$BINUTILS_INCDIR$ac_delim
+INTERNAL_PREFIX!$INTERNAL_PREFIX$ac_delim
 NM!$NM$ac_delim
 ifGNUmake!$ifGNUmake$ac_delim
 LN_S!$LN_S$ac_delim
@@ -22017,7 +22031,7 @@
 LTLIBOBJS!$LTLIBOBJS$ac_delim
 _ACEOF
 
-  if test `sed -n "s/.*$ac_delim\$/X/p" conf$$subs.sed | grep -c X` = 90; then
+  if test `sed -n "s/.*$ac_delim\$/X/p" conf$$subs.sed | grep -c X` = 91; then
     break
   elif $ac_last_try; then
     { { echo "$as_me:$LINENO: error: could not make $CONFIG_STATUS" >&5