Bugfix: CommonLibrary error with multiple library types

When XXX_LIBRARY_TYPE is a list, e.g. STATIC;SHARED, CMake
fails on line 94.

This patch stops CMake from failing, but does not address the
correct behaviour for MSVC when both shared and static libraries
are requested.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	CommonLibrary.cmake
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Fix regression: multiple use of CommonCPPCTest

MGL uses CommonCPPCTest in more than one test sub-directory,
using the functionality introduced in #d081493. Commit #603eeb5
breaks this capability. This patch creates the
${PROJECT_NAME}_run_cpp_tests target only if it does not
already exist.
Merge pull request #247 from halfflat/bugfix-commoncppctest-multiple-dirs

Bugfix commoncppctest multiple dirs