* 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)
irengrig