[ML] Investigate replacing uses of bash and other Unix tools in CMake build system with platform independent code

The initial approach to migrating to a `CMake` build system has continued to assume the presence of a Unix like build environment. On Windows this requires the presence of `git bash` and the minimal GNU toolset - `MinGW`. It is desirable to lessen the dependency on such tools on Windows as it lowers the bar for developers on that platform and simplifies the setting up of the build environment.

What follows is a list of places in the `CMake` build system that make calls to `bash` or other Unix commands.

### `lib/ver/CMakeLists.txt`
```
lib/ver/CMakeLists.txt:execute_process(COMMAND date "+%Y" OUTPUT_VARIABLE BUILD_YEAR OUTPUT_STRIP_TRAILING_WHITESPACE)
lib/ver/CMakeLists.txt:execute_process(COMMAND id COMMAND awk -F ")" "{ print $1 }" COMMAND awk -F "(" "{ print $2 }" OUTPUT_VARIABLE USER_NAME
lib/ver/CMakeLists.txt:execute_process(COMMAND awk -F= "/elasticsearchVersion/ {gsub(/-.*/,\"\"); print $2}" $ENV{CPP_SRC_HOME}/gradle.properties OUTPUT_VARIABLE PRODUCT_VERSION OUTPUT_STRIP_TRAILING_WHITESPACE)
```

Suggestions:
* id: Use native “whoami” command that gives response "vm-win2016-64-1\eds” and parse using cmake string commands
* date: use native “date /T” (requires extensions to be installed and parse out the year
* awk: use CMake file READ command to read in gradle.properties and then search and parse out elasticsearchVersion value

### `3rd_party/CMakeLists.txt:`
```
add_custom_target(
eigen
DEPENDS 3rd_party.sh pull-eigen.sh
COMMAND bash -c "./3rd_party.sh --add ${INSTALL_DIR}"
COMMAND bash -c "./pull-eigen.sh"
WORKING_DIRECTORY cmake${CMAKE_CURRENT_SOURCE_DIR}
)
```

### `cmake/compiler/vs2019.cmake`
```
execute_process(COMMAND bash -c "cygpath -m -s \"${ROOT}/Program Files (x86)/Microsoft Visual Studio/2019/Professional\"" OUTPUT_VARIABLE VCBASE OUTPUT_STRIP_TRAILING_WHITESPACE)
execute_process(COMMAND bash -c "cygpath -m -s \"${ROOT}/Program Files (x86)/Windows Kits\"" OUTPUT_VARIABLE WINSDKBASE OUTPUT_STRIP_TRAILING_WHITESPACE)
execute_process(COMMAND bash -c "cygpath -m -s \"${ROOT}/Program Files (x86)\"" OUTPUT_VARIABLE PFX86_DIR OUTPUT_STRIP_TRAILING_WHITESPACE)
execute_process(COMMAND bash -c "cd ${PFX86_DIR} && cygpath -m -s \"Microsoft Visual Studio\"" OUTPUT_VARIABLE MSVC_DIR OUTPUT_STRIP_TRAILING_WHITESPACE)
execute_process(COMMAND bash -c "cd ${PFX86_DIR} && cygpath -m -s \"Windows Kits\"" OUTPUT_VARIABLE WIN_KITS_DIR OUTPUT_STRIP_TRAILING_WHITESPACE)
execute_process(COMMAND bash -c "/bin/ls -1 ${PFX86_DIR}/${MSVC_DIR}/2019/Professional/VC/Tools/MSVC" COMMAND bash -c "tail -1" OUTPUT_VARIABLE VCVER OUTPUT_STRIP_TRAILING_WHITESPACE)
execute_process(COMMAND bash -c "/bin/ls -1 ${WINSDKBASE}/10/Include" COMMAND bash -c "tail -1" OUTPUT_VARIABLE UCRTVER OUTPUT_STRIP_TRAILING_WHITESPACE)
```

### `cmake/variables.cmake`
```
execute_process(COMMAND awk -F= "/elasticsearchVersion/ {gsub(/-.*/,\"\"); print $2}"
$ENV{CPP_SRC_HOME}/gradle.properties OUTPUT_VARIABLE ML_VERSION_NUM OUTPUT_STRIP_TRAILING_WHITESPACE)
```

### `cmake/functions.cmake`
```
function(ml_generate_resources _target)
if(NOT WIN32)
return()
endif()
set( ${_target}_LINKFLAGS ${CMAKE_CURRENT_BINARY_DIR}/${_target}.res )
set_target_properties( ${_target} PROPERTIES LINK_FLAGS ${${_target}_LINKFLAGS} )
execute_process(COMMAND bash -c "${CMAKE_SOURCE_DIR}/mk/make_rc_defines.sh ${_target}.exe" OUTPUT_VARIABLE
RC_DEFINES OUTPUT_STRIP_TRAILING_WHITESPACE)
file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/tmp.sh "rc -nologo ${CPPFLAGS} ${RC_DEFINES} -Fo${_target}.res ${CMAKE_SOURCE_DIR}/mk/ml.rc")
add_custom_target(
${_target}.res
DEPENDS ${CMAKE_SOURCE_DIR}/mk/ml.rc ${CMAKE_SOURCE_DIR}/gradle.properties ${CMAKE_SOURCE_DIR}/mk/ml.ico ${CMAKE_SOURCE_DIR}/mk/make_rc_defines.sh ${CMAKE_CURRENT_BINARY_DIR}/tmp.sh
COMMAND bash -c ${CMAKE_CURRENT_BINARY_DIR}/tmp.sh
)
add_dependencies(${_target} ${_target}.res)

set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES ${CMAKE_CURRENT_BINARY_DIR}/tmp.sh)
set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES ${CMAKE_CURRENT_BINARY_DIR}/${_target}.res)
endfunction()
```

### `build.gradle`
```
grep -n bash build.gradle
83:// Always do the C++ build using bash (Git bash on Windows)
84:project.ext.bash = isWindows ? "C:\\Program Files\\Git\\bin\\bash" : "/bin/bash"
102: commandLine bash
111: commandLine bash
118: commandLine bash
126: commandLine bash
133: commandLine bash
192: commandLine bash
400: commandLine bash
```