The "tools-prefix" method for building world with clang.

First of all, Makefile.inc1 is modified to build the clang libraries and
binaries during the cross-tools stage, iff CC=clang.

The lib/clang/clang.build.mk file, which contains common build settings
for all llvm and clang sources, is modified to add a CLANG_PREFIX macro
to CFLAGS, iff TOOLS_PREFIX is defined.

In the clang sources, the files that define the built-in search paths
for headers, startup objects and libraries, are modified to use the
(optional) CLANG_PREFIX macro as prefix for all those paths.


diff --git a/Makefile.inc1 b/Makefile.inc1
index d2581c5..6e58396 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -1078,8 +1078,15 @@ _kgzip=		usr.sbin/kgzip
 .endif
 .endif
 
+.if ${CC:T:Mclang} == "clang"
+_clang=		usr.bin/clang
+_clang_libs=	lib/clang
+.endif
+
 cross-tools:
 .for _tool in \
+    ${_clang_libs} \
+    ${_clang} \
     gnu/usr.bin/binutils \
     gnu/usr.bin/cc \
     usr.bin/xlint/lint1 usr.bin/xlint/lint2 usr.bin/xlint/xlint \
diff --git a/contrib/llvm/tools/clang/lib/Driver/ToolChains.cpp b/contrib/llvm/tools/clang/lib/Driver/ToolChains.cpp
index a78d153..3506590 100644
--- a/contrib/llvm/tools/clang/lib/Driver/ToolChains.cpp
+++ b/contrib/llvm/tools/clang/lib/Driver/ToolChains.cpp
@@ -26,6 +26,10 @@
 
 #include <cstdlib> // ::getenv
 
+#ifndef CLANG_PREFIX
+#define CLANG_PREFIX
+#endif
+
 using namespace clang::driver;
 using namespace clang::driver::toolchains;
 
@@ -869,11 +873,9 @@ FreeBSD::FreeBSD(const HostInfo &Host, const llvm::Triple& Triple, bool Lib32)
   getProgramPaths().push_back(getDriver().Dir + "/../libexec");
   getProgramPaths().push_back("/usr/libexec");
   if (Lib32) {
-    getFilePaths().push_back(getDriver().Dir + "/../lib32");
-    getFilePaths().push_back("/usr/lib32");
+    getFilePaths().push_back(CLANG_PREFIX "/usr/lib32");
   } else {
-    getFilePaths().push_back(getDriver().Dir + "/../lib");
-    getFilePaths().push_back("/usr/lib");
+    getFilePaths().push_back(CLANG_PREFIX "/usr/lib");
   }
 }
 
diff --git a/contrib/llvm/tools/clang/lib/Frontend/InitHeaderSearch.cpp b/contrib/llvm/tools/clang/lib/Frontend/InitHeaderSearch.cpp
index fcfee71..9187148 100644
--- a/contrib/llvm/tools/clang/lib/Frontend/InitHeaderSearch.cpp
+++ b/contrib/llvm/tools/clang/lib/Frontend/InitHeaderSearch.cpp
@@ -30,6 +30,9 @@
   #define WIN32_LEAN_AND_MEAN 1
   #include <windows.h>
 #endif
+#ifndef CLANG_PREFIX
+#define CLANG_PREFIX
+#endif
 using namespace clang;
 using namespace clang::frontend;
 
@@ -408,9 +411,10 @@ static bool getWindowsSDKDir(std::string &path) {
 
 void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
                                             const HeaderSearchOptions &HSOpts) {
-#if 0 /* Remove unneeded include paths. */
   // FIXME: temporary hack: hard-coded paths.
-  AddPath("/usr/local/include", System, true, false, false);
+#ifndef __FreeBSD__
+  AddPath(CLANG_PREFIX "/usr/local/include", System, true, false, false);
+#endif
 
   // Builtin includes use #include_next directives and should be positioned
   // just prior C include dirs.
@@ -421,7 +425,6 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
     P.appendComponent("include");
     AddPath(P.str(), System, false, false, false, /*IgnoreSysRoot=*/ true);
   }
-#endif
 
   // Add dirs specified via 'configure --with-c-include-dirs'.
   llvm::StringRef CIncludeDirs(C_INCLUDE_DIRS);
@@ -518,13 +521,15 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
   case llvm::Triple::MinGW32:
     AddPath("c:/mingw/include", System, true, false, false);
     break;
+  case llvm::Triple::FreeBSD:
+    AddPath(CLANG_PREFIX "/usr/include/clang/" CLANG_VERSION_STRING,
+      System, false, false, false);
+    break;
   default:
     break;
   }
 
-  AddPath("/usr/include/clang/" CLANG_VERSION_STRING,
-    System, false, false, false);
-  AddPath("/usr/include", System, false, false, false);
+  AddPath(CLANG_PREFIX "/usr/include", System, false, false, false);
 }
 
 void InitHeaderSearch::
@@ -726,8 +731,10 @@ AddDefaultCPlusPlusIncludePaths(const llvm::Triple &triple) {
   case llvm::Triple::FreeBSD:
     // FreeBSD 8.0
     // FreeBSD 7.3
-    AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2", "", "", "", triple);
-    AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2/backward", "", "", "", triple);
+    AddGnuCPlusPlusIncludePaths(CLANG_PREFIX "/usr/include/c++/4.2",
+                                "", "", "", triple);
+    AddGnuCPlusPlusIncludePaths(CLANG_PREFIX "/usr/include/c++/4.2/backward",
+                                "", "", "", triple);
     break;
   case llvm::Triple::Minix:
     AddGnuCPlusPlusIncludePaths("/usr/gnu/include/c++/4.4.3",
diff --git a/lib/clang/clang.build.mk b/lib/clang/clang.build.mk
index 6351eda..86384db 100644
--- a/lib/clang/clang.build.mk
+++ b/lib/clang/clang.build.mk
@@ -28,6 +28,10 @@ LLVM_REQUIRES_RTTI=
 CFLAGS+=-fno-rtti
 .endif
 
+.ifdef TOOLS_PREFIX
+CFLAGS+=-DCLANG_PREFIX=\"${TOOLS_PREFIX}\"
+.endif
+
 .PATH:	${LLVM_SRCS}/${SRCDIR}
 
 TBLGEN=tblgen ${CFLAGS:M-I*}