CMake: Fix building libraries on macOS

When building libraries on macOS they'd be missing the SONAME
attribute which causes the linker to embed relative paths into
other libraries and executables:

Dynamic section at offset 0x52794 contains 28 entries:
 Type     Name/Value
(NEEDED) Shared library: [libgcc_s.so]
(NEEDED) Shared library: [Userland/Libraries/LibCrypt/libcrypt.so]
(NEEDED) Shared library: [Userland/Libraries/LibCrypto/libcrypto.so]
(NEEDED) Shared library: [Userland/Libraries/LibC/libc.so]
(NEEDED) Shared library: [libsystem.so]
(NEEDED) Shared library: [libm.so]
(NEEDED) Shared library: [libc.so]

The dynamic linker then fails to load those libraries which makes
the system unbootable.

CMakeLists.txt

@@ -140,9 +140,10 @@ foreach(lang ASM C CXX OBJC OBJCXX)
  unset(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG)
  unset(CMAKE_${lang}_SYSROOT_FLAG)
  if (CMAKE_SYSTEM_NAME MATCHES Darwin)
- ## MacOS Workaround. Don't generate install_name flag when cross compiling
+ ## macOS workaround. Use GNU ld flags for SONAMEs.
  set(CMAKE_${lang}_CREATE_SHARED_LIBRARY
- "<CMAKE_${lang}_COMPILER> <LANGUAGE_COMPILE_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS> <LINK_FLAGS> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>")
+ "<CMAKE_${lang}_COMPILER> <LANGUAGE_COMPILE_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS> <LINK_FLAGS> <SONAME_FLAG><TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>")
+ set(CMAKE_SHARED_LIBRARY_SONAME_${lang}_FLAG "-Wl,-soname,")
  endif()
 endforeach()