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[sbc100]

rebase

clang/lib/Driver/Driver.cpp

: Diags(Diags), VFS(std::move(VFS)), Mode(GCCMode),
       CCLogDiagnostics(false), CCGenDiagnostics(false),
       TargetTriple(TargetTriple), CCCGenericGCCName(""), Saver(Alloc),
       CheckInputsExist(true), GenReproducer(false),
       SuppressMissingInputWarning(false) {
   // Provide a sane fallback if no VFS is specified.
   if (!this->VFS)
     this->VFS = llvm::vfs::getRealFileSystem();
 
-  if (llvm::sys::path::is_relative(SysRoot)) {
-    SysRoot = GetResourcesPath(ClangExecutable, SysRoot);
-  }
-
   Name = std::string(llvm::sys::path::filename(ClangExecutable));
   Dir = std::string(llvm::sys::path::parent_path(ClangExecutable));
   InstalledDir = Dir; // Provide a sensible default installed dir.
 
+  if (llvm::sys::path::is_relative(SysRoot)) {
+    // Prepend InstalledDir if SysRoot is relative
+    SmallString<128> fullpath(InstalledDir);
+    llvm::sys::path::append(fullpath, SysRoot);
+    SysRoot = std::string(fullpath);
+  }
+
 #if defined(CLANG_CONFIG_FILE_SYSTEM_DIR)
   SystemConfigDir = CLANG_CONFIG_FILE_SYSTEM_DIR;
 #endif
 #if defined(CLANG_CONFIG_FILE_USER_DIR)
   UserConfigDir = CLANG_CONFIG_FILE_USER_DIR;
 #endif
 
   // Compute the path to the resource directory.