[BOLT] Enable standalone build (#97130)

Continue from #87196 as author did not have much time, I have taken over
working on this PR. We would like to have this so it'll be easier to
package for Nix.

Can be tested by copying cmake, bolt, third-party, and llvm directories
out into their own directory with this PR applied and then build bolt.

---------

Co-authored-by: pca006132 <john.lck40@gmail.com>

1 files changed, 29 insertions, 6 deletions

diff --git a/bolt/lib/RuntimeLibs/RuntimeLibrary.cpp b/bolt/lib/RuntimeLibs/RuntimeLibrary.cpp
index 276b034..336c676 100644
--- a/bolt/lib/RuntimeLibs/RuntimeLibrary.cpp
+++ b/bolt/lib/RuntimeLibs/RuntimeLibrary.cpp
@@ -26,8 +26,8 @@ using namespace bolt;
 
 void RuntimeLibrary::anchor() {}
 
-std::string RuntimeLibrary::getLibPath(StringRef ToolPath,
-                                       StringRef LibFileName) {
+std::string RuntimeLibrary::getLibPathByToolPath(StringRef ToolPath,
+                                                 StringRef LibFileName) {
   StringRef Dir = llvm::sys::path::parent_path(ToolPath);
   SmallString<128> LibPath = llvm::sys::path::parent_path(Dir);
   llvm::sys::path::append(LibPath, "lib" LLVM_LIBDIR_SUFFIX);
@@ -38,13 +38,36 @@ std::string RuntimeLibrary::getLibPath(StringRef ToolPath,
     llvm::sys::path::append(LibPath, "lib" LLVM_LIBDIR_SUFFIX);
   }
   llvm::sys::path::append(LibPath, LibFileName);
-  if (!llvm::sys::fs::exists(LibPath)) {
-    errs() << "BOLT-ERROR: library not found: " << LibPath << "\n";
-    exit(1);
-  }
   return std::string(LibPath);
 }
 
+std::string RuntimeLibrary::getLibPathByInstalled(StringRef LibFileName) {
+  SmallString<128> LibPath(CMAKE_INSTALL_FULL_LIBDIR);
+  llvm::sys::path::append(LibPath, LibFileName);
+  return std::string(LibPath);
+}
+
+std::string RuntimeLibrary::getLibPath(StringRef ToolPath,
+                                       StringRef LibFileName) {
+  if (llvm::sys::fs::exists(LibFileName)) {
+    return std::string(LibFileName);
+  }
+
+  std::string ByTool = getLibPathByToolPath(ToolPath, LibFileName);
+  if (llvm::sys::fs::exists(ByTool)) {
+    return ByTool;
+  }
+
+  std::string ByInstalled = getLibPathByInstalled(LibFileName);
+  if (llvm::sys::fs::exists(ByInstalled)) {
+    return ByInstalled;
+  }
+
+  errs() << "BOLT-ERROR: library not found: " << ByTool << ", " << ByInstalled
+         << ", or " << LibFileName << "\n";
+  exit(1);
+}
+
 void RuntimeLibrary::loadLibrary(StringRef LibPath, BOLTLinker &Linker,
                                  BOLTLinker::SectionsMapper MapSections) {
   ErrorOr<std::unique_ptr<MemoryBuffer>> MaybeBuf =