Export compiler related constants from CMake

.gitignore

@@ -1,5 +1,6 @@
 # CMake
 build/
+_buildconfig.py
 
 # Cargo
 target/

CMakeLists.txt

@@ -50,6 +50,9 @@ execute_process(
 )
 message(STATUS ${CLANG_OUTPUT})
 
+include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/generate-buildconfig-py.cmake)
+generate_buildconfig_py("${CMAKE_CURRENT_SOURCE_DIR}/tests/lit/lit")
+
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/rust-toolchain.cmake)
 set(RUST_STAMP_FILE "${CMAKE_BINARY_DIR}/.rust-toolchain.stamp")
 

cmake/generate-buildconfig-py.cmake

@@ -0,0 +1,15 @@
+function(generate_buildconfig_py outdir)
+  file(CONFIGURE
+    OUTPUT "${outdir}/_buildconfig.py"
+    CONTENT [[
+"""Generated by CMake, do not edit."""
+
+from pathlib import Path
+
+CXX = Path(r"@CMAKE_CXX_COMPILER@")
+CC = Path(r"@CMAKE_C_COMPILER@")
+]]
+    ESCAPE_QUOTES
+    @ONLY
+  )
+endfunction()

tests/lit/lit/formats/Cpp2RustTest.py

@@ -3,6 +3,7 @@
 
 import lit.Test
 import lit.util
+from .._buildconfig import CXX, CC
 from .base import TestFormat
 from dataclasses import dataclass
 from pathlib import Path
@@ -177,12 +178,7 @@ def build_cpp(self):
             self.cpp_bin = self.build_dir / "app"
             return None
 
-        ## FIXME: these must use the detected/chosen compiler in cmake
-        cc = (
-            os.environ.get("CC", "clang")
-            if self.cc_input.suffix == ".c"
-            else os.environ.get("CXX", "clang++")
-        )
+        cc = CC if self.cc_input.suffix == ".c" else CXX
         self.cpp_bin = self.tmp_dir / "cpp"
         cmd = [
             cc,