Split libpkl libraries between shared and static libs (#1812)

This adds a `libpkl-static.pc` so pkg-config users can link either
statically or dynamically via `pkg-config --libs libpkl`, or
`pkg-config --libs libpkl-static`.

Additionally, this fixes an issue where the replace tokens wasn't
doing anything, leaving the `@version@` token intact in the archive.

Additionally, this adds an `-install_name` when building the dylib for macOS.

Co-authored-by: Islon Scherer <islonscherer@gmail.com>

libpkl/src/main/files/lib/pkgconfig/libpkl-static.pc

@@ -0,0 +1,11 @@
+prefix=${pcfiledir}/../..
+exec_prefix=${prefix}
+libdir=${exec_prefix}/lib
+includedir=${prefix}/include
+
+Name: libpkl
+Description: C library for calling into Pkl's message passing API.
+URL: https://pkl-lang.org/main/current/libpkl/index.html
+Version: @version@
+Libs: ${libdir}/@static_lib_filename@@extra_static_libs@
+Cflags: -I${includedir}

libpkl/src/main/files/lib/pkgconfig/libpkl.pc

@@ -7,5 +7,5 @@ Name: libpkl
 Description: C library for calling into Pkl's message passing API.
 URL: https://pkl-lang.org/main/current/libpkl/index.html
 Version: @version@
-Libs: -L${libdir} -lpkl -lz -lpthread
+Libs: -L${libdir}@extra_shared_libs@
 Cflags: -I${includedir}