Bring back defines and flags

Several definitions and flags were dropped from the build when moving to
swift-froundation.
This patch puts back the ones that we need in order to build against
musl.

Since the musl builds are static, we also need to pick up the link to
libRT or dispatch will fail to link.

Author: etcwilde

CMakeLists.txt

@@ -95,9 +95,29 @@ endif()
 FetchContent_MakeAvailable(SwiftFoundationICU SwiftFoundation)
 
 include(CheckLinkerFlag)
+include(CheckSymbolExists)
 
 check_linker_flag(C "LINKER:--build-id=sha1" LINKER_SUPPORTS_BUILD_ID)
 
+check_symbol_exists("strlcat" "string.h" HAVE_STRLCAT)
+check_symbol_exists("strlcpy" "string.h" HAVE_STRLCPY)
+check_symbol_exists("issetugid" "unistd.h" HAVE_ISSETUGID)
+add_compile_definitions(
+  $<$<AND:$<COMPILE_LANGUAGE:C>,$<BOOL:${HAVE_STRLCAT}>>:HAVE_STRLCAT>
+  $<$<AND:$<COMPILE_LANGUAGE:C>,$<BOOL:${HAVE_STRLCPY}>>:HAVE_STRLCPY>
+  $<$<AND:$<COMPILE_LANGUAGE:C>,$<BOOL:${HAVE_ISSETUGID}>>:HAVE_ISSETUGID>)
+
+if(CMAKE_SYSTEM_NAME STREQUAL Linux OR ANDROID)
+  add_compile_definitions($<$<COMPILE_LANGUAGE:C>:_GNU_SOURCE>)
+endif()
+
+if(CMAKE_SYSTEM_NAME STREQUAL Linux)
+  check_symbol_exists(sched_getaffinity "sched.h" HAVE_SCHED_GETAFFINITY)
+  add_compile_definitions($<$<COMPILE_LANGUAGE:C>:HAVE_SCHED_GETAFFINITY>)
+endif()
+
+add_compile_options($<$<COMPILE_LANGUAGE:C>:-fblocks>)
+
 # Precompute module triple for installation
 if(NOT SwiftFoundation_MODULE_TRIPLE)
     set(module_triple_command "${CMAKE_Swift_COMPILER}" -print-target-info)
@@ -114,6 +134,7 @@ endif()
 
 # We know libdispatch is always unavailable on WASI
 if(NOT CMAKE_SYSTEM_NAME STREQUAL WASI)
+    find_package(LibRT)
     find_package(dispatch CONFIG)
     if(NOT dispatch_FOUND)
         if(CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL "Android")

cmake/modules/FindLibRT.cmake

@@ -4,7 +4,7 @@
 #
 # Find librt library and headers.
 #
-# The mdoule defines the following variables:
+# The module defines the following variables:
 #
 # ::
 #