Define Python_FIND_VIRTUALENV in addition to Python3_FIND_VIRTUALENV (#4004)

MLIR searches for both Python3 and Python. If both variables are not
defined equally and there multiple python versions on the system, CMake
may behave really weirdly.

More details here: llvm/llvm-project#126162

So I grepped for all instances of `Python3_FIND_VIRTUALENV` and added
similar `Python_FIND_VIRTUALENV` definition.

Author: dbabokin

build_tools/e2eshark_build.sh

@@ -21,6 +21,7 @@ cmake -S "$repo_root/externals/llvm-project/llvm" -B "$build_dir" \
   -GNinja \
   -DCMAKE_BUILD_TYPE=Release \
   -DPython3_FIND_VIRTUALENV=ONLY \
+  -DPython_FIND_VIRTUALENV=ONLY \
   -DLLVM_ENABLE_PROJECTS=mlir \
   -DLLVM_EXTERNAL_PROJECTS="torch-mlir" \
   -DLLVM_EXTERNAL_TORCH_MLIR_SOURCE_DIR="$PWD" \

build_tools/python_deploy/build_windows_ci.sh

@@ -33,6 +33,7 @@ cmake -GNinja -Bbuild \
   -DLLVM_TARGETS_TO_BUILD=host \
   -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
   -DPython3_FIND_VIRTUALENV=ONLY \
+  -DPython_FIND_VIRTUALENV=ONLY \
   -DLLVM_EXTERNAL_PROJECTS="torch-mlir" \
   -DLLVM_EXTERNAL_TORCH_MLIR_SOURCE_DIR="$PWD" \
   -DPython3_EXECUTABLE="$(which python)" \

docs/development.md

@@ -105,6 +105,7 @@ sudo apt install clang ccache lld
           -DCMAKE_BUILD_TYPE=RelWithDebInfo \
           -DLLVM_ENABLE_ASSERTIONS=ON \
           -DPython3_FIND_VIRTUALENV=ONLY \
+          -DPython_FIND_VIRTUALENV=ONLY \
           -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
           -DLLVM_TARGETS_TO_BUILD=host \
           `# For building LLVM "in-tree"` \
@@ -123,6 +124,7 @@ sudo apt install clang ccache lld
           -DCMAKE_BUILD_TYPE=RelWithDebInfo \
           -DLLVM_ENABLE_ASSERTIONS=ON \
           -DPython3_FIND_VIRTUALENV=ONLY \
+          -DPython_FIND_VIRTUALENV=ONLY \
           -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
           -DLLVM_TARGETS_TO_BUILD=host \
           `# For building LLVM "out-of-tree"` \

setup.py

@@ -113,6 +113,8 @@ def cmake_build(self, cmake_build_dir):
             f"-DCMAKE_BUILD_TYPE={CMAKE_BUILD_TYPE}",
             f"-DPython3_EXECUTABLE={sys.executable}",
             f"-DPython3_FIND_VIRTUALENV=ONLY",
+            f"-DPython_EXECUTABLE={sys.executable}",
+            f"-DPython_FIND_VIRTUALENV=ONLY",
             f"-DMLIR_ENABLE_BINDINGS_PYTHON=ON",
             f"-DLLVM_TARGETS_TO_BUILD=host",
             f"-DLLVM_ENABLE_ZSTD=OFF",