Build: Fix RPATH handling

CMAKE_INSTALL_RPATH has to be set before the targets are defined (oops.)

This also explicitly turns on MACOSX_RPATH for the shared libraries
(which is the default with newer versions of CMake but not with 2.8.x.)
The old autotools/libtool build system hard-coded the install name
directory of the OS X shared libraries to libdir, which meant that any
executable that linked against those libraries would also be hard-coded
to look for the libjpeg-turbo libraries in that directory.  @rpath makes
the OS X version of libjpeg-turbo behave like the Linux version, in the
sense that the executables under /opt/libjpeg-turbo/bin will
automatically pick up the libraries under /opt/libjpeg-turbo/lib* by
default, but other executables won't unless they are linked with -rpath.

CMakeLists.txt

@@ -124,6 +124,7 @@ else()
 endif()
 set(LIBDIR ${DEFAULT_LIBDIR} CACHE PATH
   "Directory into which libraries should be installed (default: ${DEFAULT_LIBDIR})")
+set(CMAKE_INSTALL_RPATH ${LIBDIR})
 
 foreach(var CMAKE_INSTALL_PREFIX BINDIR DATADIR DOCDIR INCLUDEDIR LIBDIR)
   message(STATUS "${var} = ${${var}}")
@@ -573,6 +574,9 @@ if(WITH_TURBOJPEG)
     if(MINGW)
       set_target_properties(turbojpeg PROPERTIES LINK_FLAGS -Wl,--kill-at)
     endif()
+    if(APPLE)
+      set_target_properties(turbojpeg PROPERTIES MACOSX_RPATH 1)
+    endif()
     set_target_properties(turbojpeg PROPERTIES
       SOVERSION ${TURBOJPEG_SO_MAJOR_VERSION} VERSION ${TURBOJPEG_SO_VERSION})
     if(TJMAPFLAG)
@@ -1278,7 +1282,6 @@ endif()
 if(WIN32)
   set(EXE ".exe")
 endif()
-SET(CMAKE_INSTALL_RPATH ${LIBDIR})
 
 if(WITH_TURBOJPEG)
   if(ENABLE_SHARED)

sharedlib/CMakeLists.txt

@@ -40,6 +40,9 @@ add_library(jpeg SHARED ${JPEG_SRCS} ${DEFFILE} $<TARGET_OBJECTS:simd>
 
 set_target_properties(jpeg PROPERTIES SOVERSION ${SO_MAJOR_VERSION}
   VERSION ${SO_MAJOR_VERSION}.${SO_AGE}.${SO_MINOR_VERSION})
+if(APPLE)
+  set_target_properties(jpeg PROPERTIES MACOSX_RPATH 1)
+endif()
 if(MAPFLAG)
   set_target_properties(jpeg PROPERTIES
     LINK_FLAGS "${MAPFLAG}${CMAKE_BINARY_DIR}/libjpeg.map")