The ExportImport test drives its Export and Import projects using the
same compiler and flags. This converts the ctest --build-and-test
command lines to use an initial cache file instead of passing all
settings on the command line.
We need a shorter command line to pass through VS 6 on Win98.
This approach reduces duplicate code anyway.
This extends the ExportImport test. The Export project creates a C++
static library and exports it. Then the Import project links the
library into a C executable. On most platforms the executable will link
only if the C++ linker is chosen correctly.