mx/unittest: fix cygwin path issue

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extra : rebase_source : 44db38be48e06e0bb51837c66f21cf52885172bc
amd64hotspot: guard foreign call registration with the according flag
graalCompiler: fix bootstrap with CTW (regression caused by jdk8-8041959)

--HG--
extra : amend_source : 6b07b23f9c984830e085c1fdce8a7bf4776df880
graal/hotspot: fix memleak
refactored GraalCompilerTest API to be in terms of ResolvedJavaMethod instead of Method