Add BAZEL.md file with build and test instructions on all supported platforms.
Bug: skia:12400
Change-Id: If284558ccc34af3d7016ccf1df0b8f24cf51ce91
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/444976
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Leandro Lovisolo <lovisolo@google.com>
diff --git a/BAZEL.md b/BAZEL.md
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+# SkCMS Bazel build
+
+This file provides instructions on how to build and test SkCMS using
+[Bazel](https://bazel.build).
+
+## Linux
+
+### Building and testing locally
+
+Open a terminal and `cd` into your SkCMS repository checkout, then run:
+
+```
+$ bazel build //...
+
+$ bazel test //...
+```
+
+### Building and testing on RBE
+
+TODO(lovisolo): Add instructions after
+[this CL](https://skia-review.googlesource.com/c/skcms/+/437918) lands.
+
+## macOS
+
+TODO(lovisolo)
+
+## Windows
+
+SkCMS can be compiled with either
+[Microsoft Build Tools for Visual Studio 2019](https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2019)
+or [Clang](https://clang.llvm.org/).
+
+Before continuing, install Bazel by following the instructions
+[here](https://docs.bazel.build/versions/4.2.1/install-windows.html). Make sure
+to include `bazel` binary in your `PATH`.
+
+Note that Bazel requires symlink support to function properly. Enable symlink
+support by enabling
+[Developer Mode](https://docs.microsoft.com/en-us/windows/apps/get-started/enable-your-device-for-development),
+or by running Bazel as an administrator
+([reference](https://docs.bazel.build/versions/main/windows.html#enable-symlink-support)).
+
+### Building and testing locally
+
+The below instructions are based on the
+[Build on Windows](https://docs.bazel.build/versions/main/windows.html#build-on-windows)
+section of the Bazel documentation.
+
+#### With Build Tools for Visual Studio 2019
+
+Download and install Build Tools for Visual Studio 2019 using this
+[link](https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2019).
+Select "Desktop development with C++" on the installation wizard, and leave all
+other items unchanged.
+
+Open `cmd.exe` and `cd` into your SkCMS repository checkout. Set the `BAZEL_VC`
+environment variable to point to your Build Tools for Visual Studio 2019
+installation:
+
+```
+> set BAZEL_VC=C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC
+```
+
+Then run:
+
+```
+> bazel build //...
+
+> bazel test //... --enable_runfiles
+```
+
+Reference
+[here](https://docs.bazel.build/versions/main/windows.html#build-c-with-msvc).
+
+TODO(lovisolo): Consider adding `--enable_runfiles` to `//.bazelrc`.
+
+#### With Clang
+
+In order to build with Clang, you have to install **both** LLVM and Build Tools
+for Visual Studio 2019 (rationale
+[here](https://docs.bazel.build/versions/main/windows.html#build-c-with-clang)).
+Please install the latter by following the above instructions before proceeding.
+
+Download and install LLVM from this
+[link](https://github.com/llvm/llvm-project/releases/tag/llvmorg-12.0.1).
+
+Open `cmd.exe` and `cd` into your SkCMS repository checkout, then run:
+
+```
+> bazel build //... --compiler=clang-cl
+
+> bazel test //... --compiler=clanmg-cl --enable_runfiles
+```
+
+If the above commands fail because Bazel cannot find your LLVM installation, set
+the `BAZEL_LLVM` environment variable to point to your LLVM installation:
+
+```
+> set BAZEL_LLVM=C:\Program Files\LLVM
+```
+
+Reference
+[here](https://docs.bazel.build/versions/main/windows.html#build-c-with-clang).
+
+TODO(lovisolo): Investigate adding a platform target to the top-level
+`BUILD.bazel` file as per the instructions
+[here](https://docs.bazel.build/versions/main/windows.html#build-c-with-clang).
+
+### Building and testing on RBE
+
+TODO(lovisolo)
