deps_builder: OIIO validate deps at configure time

The last webp update changed the filenames of the webp libraries
on windows causing oiio not to find them and oiio silently build
without webp support, which only came to light after all of
blender was build and a test failed.

This change makes the OIIO validate and error out if certain
dependencies are not found at configure time so these mistakes
are caught early.

build_files/build_environment/cmake/openimageio.cmake

@@ -47,6 +47,7 @@ set(OPENIMAGEIO_EXTRA_ARGS
   -DBUILD_SHARED_LIBS=ON
   ${OPENIMAGEIO_LINKSTATIC}
   ${DEFAULT_BOOST_FLAGS}
+  -DREQUIRED_DEPS=WebP$<SEMICOLON>JPEGTurbo$<SEMICOLON>TIFF$<SEMICOLON>OpenEXR$<SEMICOLON>PNG$<SEMICOLON>OpenJPEG$<SEMICOLON>fmt$<SEMICOLON>Robinmap$<SEMICOLON>ZLIB$<SEMICOLON>pugixml$<SEMICOLON>Python
   -DUSE_LIBSQUISH=OFF
   -DUSE_QT5=OFF
   -DUSE_NUKE=OFF