[Cycles/MSVC/Testing] Fix broken test code.

Currently the tests don't run on windows for the following reasons

1) render_graph_finalize has an linking issue due missing a bunch of libraries (not sure why this is not an issue for linux)
2) This one is more interesting, in test/python/cmakelists.txt ${TEST_BLENDER_EXE_BARE} and ${TEST_BLENDER_EXE} are flat out wrong, but for some reason this doesn't matter for most tests, cause ctest will actually go out and look for the executable and fix the path for you *BUT* only for the command, if you use them in any of the parameters it'll happily pass on the wrong path.
3) on linux you can just run a .py file, windows is not as awesome and needs to be told to run it with pyton.
4) had to use the NAME/COMMAND long form of add_test otherwise $<TARGET_FILE:blender> doesn't get expanded, why? beats me.
5) missing idiff.exe for msvc2015/x64 in the libs folder.

This patch addresses 1-4 , but given I have no working Linux build environment, I'm unsure if it'll break anything there

5 has been fixed in rBL61751

Reviewers: juicyfruit, brecht, sergey

Reviewed By: sergey

Subscribers: Blendify

Tags: #cycles, #automated_testing

Differential Revision: https://developer.blender.org/D2367

make.bat

@@ -22,7 +22,7 @@ set MUST_CLEAN=
 set NOBUILD=
 set TARGET=
 set WINDOWS_ARCH=
-
+set TESTS_CMAKE_ARGS=
 :argv_loop
 if NOT "%1" == "" (
 
@@ -35,6 +35,8 @@ if NOT "%1" == "" (
 	if "%1" == "debug" (
 		set BUILD_TYPE=Debug
 	REM Build Configurations
+	) else if "%1" == "with_tests" (
+		set TESTS_CMAKE_ARGS=-DWITH_GTESTS=On
 	) else if "%1" == "full" (
 		set TARGET=Full
 		set BUILD_CMAKE_ARGS=%BUILD_CMAKE_ARGS% ^
@@ -204,7 +206,7 @@ if "%TARGET%"=="" (
 	goto HELP
 )
 
-set BUILD_CMAKE_ARGS=%BUILD_CMAKE_ARGS% -G "Visual Studio %BUILD_VS_VER% %BUILD_VS_YEAR%%WINDOWS_ARCH%"
+set BUILD_CMAKE_ARGS=%BUILD_CMAKE_ARGS% -G "Visual Studio %BUILD_VS_VER% %BUILD_VS_YEAR%%WINDOWS_ARCH%" %TESTS_CMAKE_ARGS%
 if NOT EXIST %BUILD_DIR%\nul (
 	mkdir %BUILD_DIR%
 )
@@ -284,6 +286,7 @@ goto EOF
 		echo - showhash ^(Show git hashes of source tree^)
 		echo.
 		echo Configuration options
+		echo - with_tests ^(enable building unit tests^)
 		echo - debug ^(Build an unoptimized debuggable build^)
 		echo - packagename [newname] ^(override default cpack package name^)
 		echo - x86 ^(override host autodetect and build 32 bit code^)