We have a handful of assembly files in the JDK. They have long been left aside, with a "if it ain't broken, don't fix it" attitude.

In the current panama-vector, there is a lot more assembly files incoming, including for the Windows platforrm, which has not existed for a long time in the JDK.

It is time to give assembly files some more love and care. This patch cleans up the handling in the build system, and it unifies between .s and .S files.

For historical reasons, .s has been the suffix used in the posix world to signify assembly output as generated by a compiler, and .S to signify "hand-written" precious assembly. One effect of this is that gcc and clang will run the preprocessor on files named .S but not on files named .s.

All our files are "hand-written" in this sense, and should have the .S suffix. But not all had. On mac, it was even worse, where the files were named .s but the option `-x assembler-with-cpp` was used to force clang to treat them as .S files instead...

We also had inconsistent handling on dependencies. For preprocessed assembly files, it really makes sense to have dependency tracking, exactly as for C/C++ files. Now the dependency tracking in NativeCompilation is simplified, and applies to all files. (The sole exception is Windows assembly, since masm is unable to output dependency information, even though it is able to include files :-().