Base override section names on swift version

This patch automates maintaining the right compatibility override
section names so we don't need to remember to update them by hand with
each version.

The expansions look like
'"__swift" "5" "9" "_hooks"' and
'"__s" "5" "9" "async_hook"'.

Note: The section names can only grow to be 16 characters long. If we
      see explosions regarding these names, that could be why.

Author: etcwilde

CMakeLists.txt

@@ -268,7 +268,9 @@ set(SWIFT_ANALYZE_CODE_COVERAGE FALSE CACHE STRING
 # SWIFT_VERSION is deliberately /not/ cached so that an existing build directory
 # can be reused when a new version of Swift comes out (assuming the user hasn't
 # manually set it as part of their own CMake configuration).
-set(SWIFT_VERSION "5.9")
+set(SWIFT_VERSION_MAJOR 5)
+set(SWIFT_VERSION_MINOR 9)
+set(SWIFT_VERSION "${SWIFT_VERSION_MAJOR}.${SWIFT_VERSION_MINOR}")
 
 set(SWIFT_VENDOR "" CACHE STRING
     "The vendor name of the Swift compiler")

include/swift/Runtime/CMakeConfig.h.in

@@ -7,4 +7,7 @@
 #cmakedefine01 SWIFT_BNI_OS_BUILD
 #cmakedefine01 SWIFT_BNI_XCODE_BUILD
 
+#cmakedefine SWIFT_VERSION_MAJOR "@SWIFT_VERSION_MAJOR@"
+#cmakedefine SWIFT_VERSION_MINOR "@SWIFT_VERSION_MINOR@"
+
 #endif

stdlib/public/CompatibilityOverride/CompatibilityOverride.h

@@ -85,6 +85,7 @@
 #include "swift/Runtime/Concurrency.h"
 #include "swift/Runtime/Metadata.h"
 #include "swift/Runtime/Once.h"
+#include "swift/Runtime/CMakeConfig.h"
 #include <type_traits>
 
 namespace swift {
@@ -153,8 +154,17 @@ namespace swift {
 // Override section name computation. `COMPATIBILITY_OVERRIDE_SECTION_NAME` will
 // resolve to string literal containing the appropriate section name for the
 // current library.
-#define COMPATIBILITY_OVERRIDE_SECTION_NAME_swiftRuntime "__swift58_hooks"
-#define COMPATIBILITY_OVERRIDE_SECTION_NAME_swift_Concurrency "__s58async_hook"
+// Turns into '__swift<major><minor>_hooks'
+#define COMPATIBILITY_OVERRIDE_SECTION_NAME_swiftRuntime "__swift" \
+  SWIFT_VERSION_MAJOR \
+  SWIFT_VERSION_MINOR \
+  "_hooks"
+
+// Turns into '__s<major><minor>async_hook'
+#define COMPATIBILITY_OVERRIDE_SECTION_NAME_swift_Concurrency "__s" \
+  SWIFT_VERSION_MAJOR \
+  SWIFT_VERSION_MINOR \
+  "async_hook"
 
 #define COMPATIBILITY_OVERRIDE_SECTION_NAME                                    \
   COMPATIBILITY_CONCAT(COMPATIBILITY_OVERRIDE_SECTION_NAME_,                   \