[SR-1613][SourceKit] Require blocks runtime

SourceKit makes heavy use of blocks. In order to port SourceKit to Linux,
we either need to rewrite much of it to use function pointers, or we must
require a blocks runtime. This commit requires a blocks runtime, but only
when SourceKit is being built. Currently, SourceKit is not built on Linux,
so this should not affect anyone.

Author: modocache

README.md

@@ -58,7 +58,7 @@ For OS X, you need [the latest Xcode](https://developer.apple.com/xcode/download
 
 For Ubuntu, you'll need the following development dependencies:
 
-    sudo apt-get install git cmake ninja-build clang python uuid-dev libicu-dev icu-devtools libbsd-dev libedit-dev libxml2-dev libsqlite3-dev swig libpython-dev libncurses5-dev pkg-config
+    sudo apt-get install git cmake ninja-build clang python uuid-dev libicu-dev icu-devtools libbsd-dev libedit-dev libxml2-dev libsqlite3-dev swig libpython-dev libncurses5-dev pkg-config libblocksruntime-dev
 
 **Note:** LLDB currently requires at least `swig-1.3.40` but will successfully build
 with version 2 shipped with Ubuntu.

tools/SourceKit/CMakeLists.txt

@@ -84,6 +84,11 @@ function(add_sourcekit_default_compiler_flags target)
     ANALYZE_CODE_COVERAGE "${analyze_code_coverage}"
     RESULT_VAR_NAME link_flags)
 
+  if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
+    list(APPEND c_compile_flags "-fblocks")
+    list(APPEND link_flags "-lBlocksRuntime")
+  endif()
+
   # Convert variables to space-separated strings.
   _list_escape_for_shell("${c_compile_flags}" c_compile_flags)
   _list_escape_for_shell("${link_flags}" link_flags)