Ensure bundle_libraries is called with uppercase link type

[eliemichel]

In the root CMakeLists.txt, a call to TOUPPER suggests that the value of DAWN_BUILD_MONOLITHIC_LIBRARY might have any case. However, its value is used as is in the call to bundle_libraries, which in turn uses it in a call to add_library, which requires uppercase STATICor SHARED.

This ensures that the argument passed to bundle_libraries is uppercased. Another fix could be to place a call to TOUPPERdirectly within bundle_libraries's definition.

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