nmake and jom generators no longer warn about missing INCLUDE/LIB
environment variables unless the C/CXX compiler cannot be found. This
is useful if the user does not want to use these generators with the
Visual C++ compiler, or they do not want to enable any language.
All generators now support detection of the full path to the compiler, so
require it to be so. This will allow CMake<LANG>Information.cmake and
other logic to assume the full path to the compiler tool is available.
The Makefile generators already rejected CMAKE_<LANG>_COMPILER values
that did not name an existing compiler. Extend this error message to
all generators, make it occur as early as possible, and improve the
message with advice about how to set the compiler. If the full path to
the compiler is not known, finish enabling languages with a fatal error
so configuration does not continue.
For now, allow the RC language compiler to not be a full path. Later we
will need to detect the full path to "rc" under the VS IDE.
Add a RunCMake.CompilerNotFound test to cover failure cases.
Fix the RunCMake.CompilerChange test EmptyCompiler case to work
when configuration does not continue past enable_language.
James Johnston
Brad King