Fix GMT_XXX_LIB_NAME when XXX_DLL_RENAME is set

[seisman]

For the GMT core library, the properties OUTPUT_NAME and RUNTIME_OUTPUT_NAME are set to gmt by default (e.g. libgmt.dylib, libgmt.so and gmt.dll).

For Windows, if GMT_DLL_RENAME is set, then RUNTIME_OUTPUT_NAME is changed. Thus, we can use the property RUNTIME_OUTPUT_TIME to build the variable GMT_CORE_LIB_NAME.

[seisman]

@joa-quim I add a commit on top of @PaulWessel's branch. This should fix the problem for the gmt.dll library.

[seisman]

With the changes in this PR, now we have:

Linux:

*  Build GMT core             : always [libgmt.so]
*  Build PSL library          : always [libpostscriptlight.so]
*  Build GMT supplements      : yes [supplements.so]

macOS

*  Build GMT core             : always [libgmt.dylib]
*  Build PSL library          : always [libpostscriptlight.dylib]
*  Build GMT supplements      : yes [supplements.so]

Windows (with XXX_DLL_RENAME set)

*  Build GMT core             : always [gmt_w64.dll]
*  Build PSL library          : always [postscriptlight_w64.dll]
*  Build GMT supplements      : yes [supplements_w64.dll]

[joa-quim]

Then no need to use any of the XXX_RENAME_DLL variables and just stick to the default gmt.dll, etc ...

[seisman]

Then no need to use any of the XXX_RENAME_DLL variables and just stick to the default gmt.dll, etc ...

Yes, just to test if XXX_DLL_RENAME work as we expect. I will remove them if this PR is going to be merged.

[joa-quim]

OK.

[seisman]

Now it's ready for reviewing and merging.

[joa-quim]

OK, I tested this branch and see that config.h has

/* Name of core library */
#define GMT_CORE_LIB_NAME "gmt_w64.dll"

/* Name of supplemental library */
#define GMT_SUPPL_LIBRARY "supplements_w64.dll"

/* Name of PSL library */
#define PSL_LIB_NAME "postscriptlight_w64.dll"

So all seems fine.