Improve swiftlibdir and swiftmoddir generation

linux was hardcoded, now we use OS_STRING generated in configure.ac.
Also, the build_cpu instead of the host_cpu was used for swiftmoddir,
resulting in an incorrect destination directory.

Author: gonzalolarralde

configure.ac

@@ -218,6 +218,7 @@ AM_CONDITIONAL(HAVE_SWIFT, $have_swift)
 AC_SUBST([SWIFTC])
 AC_SUBST([SWIFTC_FLAGS])
 AC_SUBST([SWIFT_LIBDIR])
+AC_SUBST([OS_STRING], ["$os_string"])
 
 #
 # Enable use of gold linker when building the Swift overlay

src/Makefile.am

@@ -3,7 +3,7 @@
 #
 
 if HAVE_SWIFT
-swiftlibdir=${prefix}/lib/swift/linux
+swiftlibdir=${prefix}/lib/swift/${OS_STRING}
 swiftlib_LTLIBRARIES=libdispatch.la
 else
 lib_LTLIBRARIES=libdispatch.la
@@ -171,7 +171,7 @@ SWIFT_GEN_FILES=	\
 	$(abs_builddir)/swift/Dispatch.swiftdoc \
 	$(SWIFT_OBJ_FILES)
 
-swiftmoddir=${prefix}/lib/swift/linux/${build_cpu}
+swiftmoddir=${prefix}/lib/swift/${OS_STRING}/${host_cpu}
 swiftmod_HEADERS=\
 	$(abs_builddir)/swift/Dispatch.swiftmodule \
 	$(abs_builddir)/swift/Dispatch.swiftdoc