Build: enable parallel source file compilation on MSVC (AcademySoftwareFoundation#2072)

By default Visual Studio projects do not compile source files in
parallel. Add "/MP" flag to enable that.

From scratch OCIO build on Ryzen 5950X, VS2022: 580sec -> 208sec.
Most of remaining single-threaded time is cloning external libraries
or building external libraries (most of them don't do parallel
compilation either). But within building OCIO itself, CPU usage
goes close to 100% instead of 5%.

Signed-off-by: Aras Pranckevicius <[email protected]>
Co-authored-by: Doug Walker <[email protected]>
Signed-off-by: Chris Nash <[email protected]>

Author: 2 people

share/cmake/utils/CompilerFlags.cmake

@@ -74,6 +74,9 @@ if(USE_MSVC)
         set(PLATFORM_COMPILE_OPTIONS "${PLATFORM_COMPILE_OPTIONS};/WX")
     endif()
 
+    # Enable parallel compilation of source files
+    set(PLATFORM_COMPILE_OPTIONS "${PLATFORM_COMPILE_OPTIONS};/MP")
+
 elseif(USE_CLANG)
 
     set(PLATFORM_COMPILE_OPTIONS "${PLATFORM_COMPILE_OPTIONS};-DUSE_CLANG")