Revert "[SkipFunctionBodies] Build everything but the stdlib with function body skipping"

Author: Harlan Haskins

cmake/modules/SwiftSource.cmake

@@ -333,11 +333,6 @@ function(_compile_swift_files
            "-emit-module-interface-path" "${interface_file}")
     endif()
 
-    if (NOT SWIFTFILE_IS_STDLIB_CORE)
-      list(APPEND swift_module_flags
-           "-Xfrontend" "-experimental-skip-non-inlinable-function-bodies")
-    endif()
-
     # If we have extra regexp flags, check if we match any of the regexps. If so
     # add the relevant flags to our swift_flags.
     if (SWIFT_EXPERIMENTAL_EXTRA_REGEXP_FLAGS OR SWIFT_EXPERIMENTAL_EXTRA_NEGATIVE_REGEXP_FLAGS)