[Shims] Include SwiftShims headers without ../

This replaces a number of `#include`-s like this:
```
#include "../../../stdlib/public/SwiftShims/Visibility.h"
```
with this:
```
#include "swift/shims/Visibility.h"
```

This is needed to allow SwiftCompilerSources to use C++ headers which include SwiftShims headers. Currently trying to do that results in errors:
```
swift/swift/include/swift/Demangling/../../../stdlib/public/SwiftShims/module.modulemap:1:8: error: redefinition of module 'SwiftShims'
module SwiftShims {
       ^
Builds.noindex/swift/swift/bootstrapping0/lib/swift/shims/module.modulemap:1:8: note: previously defined here
module SwiftShims {
       ^
```
This happens because the headers in both the source dir and the build dir refer to SwiftShims headers by relative path, and both the source root and the build root contain SwiftShims headers (which are equivalent, but since they are located in different dirs, Clang treats them as different modules).

Author: egorzhdan

CMakeLists.txt

@@ -735,6 +735,7 @@ get_filename_component(SWIFT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR} REALPATH)
 set(SWIFT_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
 set(SWIFT_CMAKE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 set(SWIFT_MAIN_INCLUDE_DIR "${SWIFT_SOURCE_DIR}/include")
+set(SWIFT_SHIMS_INCLUDE_DIR "${SWIFT_SOURCE_DIR}/stdlib/public/SwiftShims")
 set(SWIFT_INCLUDE_DIR "${CMAKE_CURRENT_BINARY_DIR}/include")
 
 set(SWIFT_RUNTIME_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin")
@@ -785,6 +786,7 @@ set(CMAKE_INCLUDE_CURRENT_DIR ON)
 include_directories(BEFORE
   ${SWIFT_MAIN_INCLUDE_DIR}
   ${SWIFT_INCLUDE_DIR}
+  ${SWIFT_SHIMS_INCLUDE_DIR}
   )
 
 # Configuration flags passed to all of our invocations of gyb.  Try to

cmake/modules/CMakeLists.txt

@@ -10,7 +10,7 @@ set(SWIFT_CONFIG_EXPORTS ${SWIFT_EXPORTS} ${SWIFT_BUILDTREE_EXPORTS})
 export(TARGETS ${SWIFT_CONFIG_EXPORTS} FILE ${SWIFT_EXPORTS_FILE})
 
 
-set(SWIFT_INCLUDE_DIRS ${SWIFT_INCLUDE_DIR} ${SWIFT_MAIN_INCLUDE_DIR})
+set(SWIFT_INCLUDE_DIRS ${SWIFT_INCLUDE_DIR} ${SWIFT_MAIN_INCLUDE_DIR} ${SWIFT_SHIMS_INCLUDE_DIR})
 set(SWIFT_LIBRARY_DIRS ${SWIFT_LIBRARY_OUTPUT_INTDIR})
 
 configure_file(

include/swift/ABI/HeapObject.h

@@ -17,6 +17,6 @@
 #ifndef SWIFT_ABI_HEAPOBJECT_H
 #define SWIFT_ABI_HEAPOBJECT_H
 
-#include "../../../stdlib/public/SwiftShims/HeapObject.h"
+#include "swift/shims/HeapObject.h"
 
 #endif // SWIFT_ABI_HEAPOBJECT_H

include/swift/ABI/KeyPath.h

@@ -22,7 +22,7 @@
 
 #include <cstdint>
 #include <cassert>
-#include "../../../stdlib/public/SwiftShims/KeyPath.h"
+#include "swift/shims/KeyPath.h"
 
 namespace swift {
 

include/swift/ABI/Metadata.h

@@ -40,7 +40,7 @@
 #include "swift/Demangling/Demangle.h"
 #include "swift/Demangling/ManglingMacros.h"
 #include "swift/Basic/Unreachable.h"
-#include "../../../stdlib/public/SwiftShims/HeapObject.h"
+#include "swift/shims/HeapObject.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Casting.h"
 

include/swift/ABI/System.h

@@ -17,6 +17,6 @@
 #ifndef SWIFT_ABI_SYSTEM_H
 #define SWIFT_ABI_SYSTEM_H
 
-#include "../../../stdlib/public/SwiftShims/System.h"
+#include "swift/shims/System.h"
 
 #endif // SWIFT_ABI_SYSTEM_H

include/swift/Demangling/Errors.h

@@ -19,8 +19,8 @@
 #ifndef SWIFT_DEMANGLING_ERRORS_H
 #define SWIFT_DEMANGLING_ERRORS_H
 
-#include "../../../stdlib/public/SwiftShims/Visibility.h"
 #include "swift/Demangling/NamespaceMacros.h"
+#include "swift/shims/Visibility.h"
 #include <inttypes.h>
 #include <stdarg.h>
 

include/swift/Runtime/Config.h

@@ -166,7 +166,7 @@ extern uintptr_t __COMPATIBILITY_LIBRARIES_CANNOT_CHECK_THE_IS_SWIFT_BIT_DIRECTL
 #endif
 
 // Bring in visibility attribute macros
-#include "../../../stdlib/public/SwiftShims/Visibility.h"
+#include "swift/shims/Visibility.h"
 
 // Define mappings for calling conventions.
 

include/swift/Runtime/Heap.h

@@ -22,7 +22,7 @@
 #include <utility>
 
 #include "swift/Runtime/Config.h"
-#include "../../../stdlib/public/SwiftShims/Visibility.h"
+#include "swift/shims/Visibility.h"
 
 namespace swift {
 // Allocate plain old memory. This is the generalized entry point

include/swift/Runtime/HeapObject.h

@@ -27,8 +27,8 @@
 #endif // SWIFT_OBJC_INTEROP
 
 // Bring in the definition of HeapObject 
-#include "../../../stdlib/public/SwiftShims/HeapObject.h"
-#include "../../../stdlib/public/SwiftShims/Visibility.h"
+#include "swift/shims/HeapObject.h"
+#include "swift/shims/Visibility.h"
 
 namespace swift {