* Extract shell fragments into a toolchain
Construct script in framework.bzl using special notation for calling
shell fragments, defining and referencing environment variables;
have the script converted from this special notation into a real script
(see README.md notes.)
The special notation is used to keep script construction in code still readable.
Tools scripts (cmake, ninja) were also converted.
* Fix reference to environment variables in examples
.. and reference it correctly $$var_name$$ so it is replaced further
* Review comments: documentation, explicitly mark functions from toolchain
- mark functions from shell toolchain as ##funname##, so that they
can not be mixed with usual shell functions
* Fix operating system name for windows in toolchain file
* Additional env vars for windows
* Correct cmake tool build
* Do not build ninja on Windows
* When run on Windows under msys, find utility from Window could "leak"...
into the script. Use heuristics to use /usr/bin/find if it exists.
Also, use pwd -W to get Windows-styled paths (for cmake)
* Add crosstool example; does not work with cmake rule yet
the code is taken from Bazel test data (bazel_toolchain_test_data)
* Make crosstool compilation of cmake_external + cc_binary work
To build example, cd examples/cmake_crosstool bazel build //:libhello_test
Changes:
1) Initially suggested in #124: put $EXT_BUILD_ROOT on path, so that relative paths can be resolved by CMake
2) Toolchain tools are references as relative paths, and they themselves refer to external repository with external/ prefix.
This will not work with CMake, as CMake also perform compiler tests and the build is performed in some temp directory.
We need to convert to absolute paths.
I did a trick with checking of $EXT_BUILD_ROOT is defined and then using it as a prefix.
3) I had to change the visibility of the cc-compiler-k8 toolchain to public
4) For CMake crosstool file, CMAKE_C_COMPILER, CMAKE_CXX_COMPILER, CMAKE_AR need to be absolute, so in cases when they are relative and not under external directory, force paths conversion
