[cmake] Fix cmake build on OSX after r250335 for older versions of cmake

[dawn]

Summary

Older versions of cmake don't support the -E env option which was added in r250335, causing the build to fail with:

[...]
[2632/2743] Linking CXX executable bin/debugserver
FAILED: : && /usr/bin/c++   -std=c++11 -stdlib=libc++ [...]
 -o bin/debugserver  lib/liblldbDebugserverCommon.a lib/liblldbUtility.a lib/liblldbDebugserverMacOSX_I386.a lib/liblldbDebugserverMacOSX_X86_64.a -framework Cocoa -Wl,-rpath,@executable_path/../lib && cd /Users/testuser/build/workspace/LLVM-Clang-LLDB_master_release_OSX/llvm/build_ninja/bin && /usr/local/Cellar/cmake/3.0.2/bin/cmake -E env CODESIGN_ALLOCATE=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/codesign_allocate codesign --force --sign lldb_codesign debugserver
CMake Error: cmake version 3.0.2
Usage: /usr/local/Cellar/cmake/3.0.2/bin/cmake -E [command] [arguments ...]
Available commands:
  chdir dir cmd [args]...   - run command in a given directory
[...]

This patch fixes this by invoking codesigning as it was before the commit if the cmake version is less than than 3.2.

[sas]

Sorry for introducing this bug. I think this is good.

lldb/trunk/tools/debugserver/source/MacOSX/CMakeLists.txt

 
 # Sign the debugserver binary
 set (CODESIGN_IDENTITY lldb_codesign)
 execute_process(
   COMMAND xcrun -f codesign_allocate
   OUTPUT_STRIP_TRAILING_WHITESPACE
   OUTPUT_VARIABLE CODESIGN_ALLOCATE
   )
+# Older cmake versions don't support "-E env".
+if (${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION} LESS 3.2)
   add_custom_command(TARGET debugserver
     POST_BUILD
-  # --entitlements option removed, as it causes errors when debugging.
-  #was: COMMAND CODESIGN_ALLOCATE=${CODESIGN_ALLOCATE} codesign --entitlements ${CMAKE_CURRENT_SOURCE_DIR}/../debugserver-entitlements.plist --force --sign ${CODESIGN_IDENTITY} debugserver
+    # Note: --entitlements option removed, as it causes errors when debugging.
+    # was: COMMAND CODESIGN_ALLOCATE=${CODESIGN_ALLOCATE} codesign --entitlements ${CMAKE_CURRENT_SOURCE_DIR}/../debugserver-entitlements.plist --force --sign ${CODESIGN_IDENTITY} debugserver
+    COMMAND CODESIGN_ALLOCATE=${CODESIGN_ALLOCATE} codesign --force --sign ${CODESIGN_IDENTITY} debugserver
+    WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/bin
+  )
+else()
+  add_custom_command(TARGET debugserver
+    POST_BUILD
+    # Note: --entitlements option removed (see comment above).
     COMMAND ${CMAKE_COMMAND} -E env CODESIGN_ALLOCATE=${CODESIGN_ALLOCATE} codesign --force --sign ${CODESIGN_IDENTITY} debugserver
     WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/bin
   )
+endif()
 
 install(TARGETS debugserver
   RUNTIME DESTINATION bin
   )