SILOptimizer: avoid trawling through the directories for includes

Use the include search path for the header search rather than
constructing the path using relative paths.  This is important for
getting the interop to work properly as well.

Author: compnerd

cmake/modules/AddSwift.cmake

@@ -779,6 +779,7 @@ function(add_libswift name)
               "-parse-as-library" ${sources}
               "-wmo" ${libswift_compile_options}
               "-I" "${SWIFT_SOURCE_DIR}/include/swift"
+              "-I" "${SWIFT_SOURCE_DIR}/include"
               "-I" "${build_dir}"
       COMMENT "Building libswift module ${module}")
 

include/swift/SILOptimizer/OptimizerBridging.h

@@ -13,7 +13,7 @@
 #ifndef SWIFT_SILOPTIMIZER_OPTIMIZERBRIDGING_H
 #define SWIFT_SILOPTIMIZER_OPTIMIZERBRIDGING_H
 
-#include "../SIL/SILBridging.h"
+#include "swift/SIL/SILBridging.h"
 
 SWIFT_BEGIN_NULLABILITY_ANNOTATIONS