Teach llvm-config about default sysroot.

[azharudd]

Summary

Prints the default sysroot if it has been set.

Patch by Azharuddin Mohammed.

[beanz]

I don't understand what you're doing here, or the justification for it. The LLVM build system has no concept of a default sysroot, and I'm not sure I understand why you're creating one. Please explain what you're trying to do and why you feel that you need this.

[azharudd]

In D25743#574916, @beanz wrote:

I don't understand what you're doing here, or the justification for it. The LLVM build system has no concept of a default sysroot, and I'm not sure I understand why you're creating one. Please explain what you're trying to do and why you feel that you need this.

I realize that the LLVM build system has no concept of default sysroot. Will abandon this change. My intention was to have a way for the user, who might be setting a default sysroot during cmake, to verify that it was set properly.

tools/llvm-config/BuildVariables.inc.in

 #define LLVM_DYLIB_COMPONENTS "@LLVM_DYLIB_COMPONENTS@"
 #define LLVM_DYLIB_VERSION "@LLVM_DYLIB_VERSION@"
 #define LLVM_HAS_GLOBAL_ISEL "@LLVM_HAS_GLOBAL_ISEL@"
+#define LLVM_DEFAULT_SYSROOT "@LLVM_DEFAULT_SYSROOT@"

tools/llvm-config/CMakeLists.txt

   set(LLVM_ENABLE_SHARED OFF)
 endif()
 string(REPLACE ";" " " LLVM_TARGETS_BUILT "${LLVM_TARGETS_TO_BUILD}")
+set(LLVM_DEFAULT_SYSROOT ${DEFAULT_SYSROOT})
 configure_file(${BUILDVARIABLES_SRCPATH} ${BUILDVARIABLES_OBJPATH} @ONLY)
 
 # Set build-time environment(s).

tools/llvm-config/llvm-config.cpp

   --components      List of all possible components.\n\
   --targets-built   List of all targets currently built.\n\
   --host-target     Target triple used to configure LLVM.\n\
+  --default-sysroot Print the default sysroot.\n\
   --build-mode      Print build mode of LLVM tree (e.g. Debug or Release).\n\
   --assertion-mode  Print assertion mode of LLVM tree (ON or OFF).\n\
   --build-system    Print the build system used to build LLVM (always cmake).\n\

         OS << '\n';
       } else if (Arg == "--targets-built") {
         OS << LLVM_TARGETS_BUILT << '\n';
+      } else if (Arg == "--default-sysroot") {
+        OS << LLVM_DEFAULT_SYSROOT << '\n';
       } else if (Arg == "--host-target") {
         OS << Triple::normalize(LLVM_DEFAULT_TARGET_TRIPLE) << '\n';
       } else if (Arg == "--build-mode") {