Add hotness data to LLVM remarks

This makes sure that if PGO is used, remarks generated using `-Zremark-dir` will include the `Hotness` attribute.

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1967,6 +1967,9 @@ extern "C" void LLVMRustContextConfigureDiagnosticHandler(
   std::unique_ptr<LLVMRemarkStreamer> LlvmRemarkStreamer;
 
   if (RemarkFilePath != nullptr) {
+    // Enable PGO hotness data for remarks, if available
+    unwrap(C)->setDiagnosticsHotnessRequested(true);
+
     std::error_code EC;
     RemarkFile = std::make_unique<ToolOutputFile>(
       RemarkFilePath,

tests/run-make/optimization-remarks-dir-pgo/Makefile

@@ -0,0 +1,16 @@
+# needs-profiler-support
+
+include ../tools.mk
+
+PROFILE_DIR=$(TMPDIR)/profiles
+
+check_hotness:
+	$(RUSTC) -Cprofile-generate="$(TMPDIR)"/profdata -O foo.rs -o$(TMPDIR)/foo
+	$(TMPDIR)/foo
+	"$(LLVM_BIN_DIR)"/llvm-profdata merge \
+		-o "$(TMPDIR)"/merged.profdata \
+		"$(TMPDIR)"/profdata/*.profraw
+	$(RUSTC) -Cprofile-use=$(TMPDIR)/merged.profdata -O foo.rs -Cremark=all -Zremark-dir=$(PROFILE_DIR)
+
+	# Check that PGO hotness is included in the remark files
+	cat $(PROFILE_DIR)/*.opt.yaml | $(CGREP) -e "Hotness"

tests/run-make/optimization-remarks-dir-pgo/foo.rs

@@ -0,0 +1,6 @@
+#[inline(never)]
+pub fn bar() {}
+
+fn main() {
+    bar();
+}