[docs] Rearrange cmake configuration options in development.md (#4110)

- emphasize the common options between "in-tree extended", "in-of-tree
base", and "out-of-tree"

Author: bjacobgordon

docs/development.md

@@ -106,16 +106,17 @@ This will build `libtorch` / `PyTorch` wheels from source and requires [the enab
 
 ```shell
 cmake -GNinja -Bbuild \
-  externals/llvm-project/llvm \
   `# Enables "--debug" and "--debug-only" flags for the "torch-mlir-opt" tool` \
   -DCMAKE_BUILD_TYPE=RelWithDebInfo \
   -DLLVM_ENABLE_ASSERTIONS=ON \
   -DPython3_FIND_VIRTUALENV=ONLY \
+  -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
+  -DLLVM_TARGETS_TO_BUILD=host \
+  `# For building LLVM "in-tree"` \
+  externals/llvm-project/llvm \
   -DLLVM_ENABLE_PROJECTS=mlir \
   -DLLVM_EXTERNAL_PROJECTS="torch-mlir" \
   -DLLVM_EXTERNAL_TORCH_MLIR_SOURCE_DIR="$PWD" \
-  -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
-  -DLLVM_TARGETS_TO_BUILD=host \
   `# use clang`\
   -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ \
   `# use ccache to cache build results` \
@@ -145,12 +146,13 @@ cmake -GNinja -Bbuild \
   -DCMAKE_BUILD_TYPE=RelWithDebInfo \
   -DLLVM_ENABLE_ASSERTIONS=ON \
   -DPython3_FIND_VIRTUALENV=ONLY \
-  -DLLVM_ENABLE_PROJECTS=mlir \
-  -DLLVM_EXTERNAL_PROJECTS="torch-mlir" \
-  -DLLVM_EXTERNAL_TORCH_MLIR_SOURCE_DIR="$PWD" \
   -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
   -DLLVM_TARGETS_TO_BUILD=host \
-  externals/llvm-project/llvm
+  `# For building LLVM "in-tree"` \
+  externals/llvm-project/llvm \
+  -DLLVM_ENABLE_PROJECTS=mlir \
+  -DLLVM_EXTERNAL_PROJECTS="torch-mlir" \
+  -DLLVM_EXTERNAL_TORCH_MLIR_SOURCE_DIR="$PWD"
 ```
 
 
@@ -163,10 +165,11 @@ cmake -GNinja -Bbuild \
   -DCMAKE_BUILD_TYPE=RelWithDebInfo \
   -DLLVM_ENABLE_ASSERTIONS=ON \
   -DPython3_FIND_VIRTUALENV=ONLY \
-  -DMLIR_DIR="$LLVM_INSTALL_DIR/lib/cmake/mlir/" \
-  -DLLVM_DIR="$LLVM_INSTALL_DIR/lib/cmake/llvm/" \
   -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
   -DLLVM_TARGETS_TO_BUILD=host \
+  `# For building LLVM "out-of-tree"` \
+  -DMLIR_DIR="$LLVM_INSTALL_DIR/lib/cmake/mlir/" \
+  -DLLVM_DIR="$LLVM_INSTALL_DIR/lib/cmake/llvm/"
   .
 ```
 The same QoL CMake flags can be used to enable clang, ccache, and lld. Be sure to have built LLVM with `-DLLVM_ENABLE_PROJECTS=mlir`.