FIX: Exclude PCM files from prefix detection on all platforms

Native linux-aarch64 builds crash with SIGSEGV in CreateInterpreter at
test time because:

1. runtime_cxxmodules defaults to ON for native builds (it was only
   set to OFF inside the cross-compilation block in build_root.sh)
2. PCM files (lib/*.pcm) are LLVM bitcode that Cling loads at startup
3. prefix_detection.ignore only excluded lib/*.pcm for non-aarch64,
   so on aarch64 rattler-build detected and relocated prefix strings
   inside the PCM files, corrupting their bitcode structure
4. Cling segfaults when loading the corrupted PCMs

The fix makes lib/*.pcm unconditionally excluded from prefix detection,
matching the existing behavior on linux-64 where native builds with
runtime_cxxmodules=ON already work.

Also reverts the CLING_CXX_PATH change from the previous commit, as
hypothesis 1 (build-time paths) was ruled out by testing.

Author: matthewfeickert

recipe/build_root.sh

@@ -332,18 +332,8 @@ else
 fi
 CMAKE_PLATFORM_FLAGS+=("-Droottest=OFF")
 
-# For native builds, use the compiler in $PREFIX (the host prefix) rather than
-# $BUILD_PREFIX. Conda's binary relocation only acts on $PREFIX paths, so
-# $BUILD_PREFIX paths baked into libCling.so would point to a nonexistent build
-# directory at runtime, causing Cling's interpreter initialization to segfault.
-# The compiler exists in $PREFIX because it is listed in the host requirements.
-if [[ "${target_platform}" == "${build_platform}" && "${target_platform}" == linux* ]]; then
-    CLING_CXX="${PREFIX}/bin/$(basename $(which $CXX))"
-else
-    CLING_CXX="$(which $CXX)"
-fi
-CMAKE_PLATFORM_FLAGS+=("-DCLING_CXX_PATH=${CLING_CXX}")
-CMAKE_PLATFORM_FLAGS+=("-DCLING_CXX_RLTV=$(basename ${CLING_CXX})")
+CMAKE_PLATFORM_FLAGS+=("-DCLING_CXX_PATH=$(which $CXX)")
+CMAKE_PLATFORM_FLAGS+=("-DCLING_CXX_RLTV=$(basename $(which $CXX))")
 
 # Now we can actually run CMake
 cmake $CMAKE_ARGS "${CMAKE_PLATFORM_FLAGS[@]}" ${SRC_DIR}/root-source

recipe/recipe.yaml

@@ -69,9 +69,9 @@ outputs:
         overdepending_behavior: ignore
       prefix_detection:
         ignore:
+          - lib/*.pcm
           - if: aarch64
             then: etc/allDict.cxx.pch
-            else: lib/*.pcm
       files:
         include:
           - "**"