stdlib: prevent static builds on Darwin

Static builds of the standard library and the SDK overlay are
unsupported post ABI stability.  Disallow building of the standard
library and SDK overlay statically for Darwin platforms.

Author: compnerd

stdlib/CMakeLists.txt

@@ -77,7 +77,12 @@ if(SWIFT_BUILD_DYNAMIC_STDLIB)
   list(APPEND SWIFT_STDLIB_LIBRARY_BUILD_TYPES SHARED)
 endif()
 if(SWIFT_BUILD_STATIC_STDLIB)
-  list(APPEND SWIFT_STDLIB_LIBRARY_BUILD_TYPES STATIC)
+  list_intersect("${SWIFT_APPLE_PLATFORMS}" "${SWIFT_SDKS}" building_darwin_sdks)
+  if(building_darwin_sdks)
+    message(SEND_ERROR "cannot build static standard library for Darwin SDKs")
+  else()
+    list(APPEND SWIFT_STDLIB_LIBRARY_BUILD_TYPES STATIC)
+  endif()
 endif()
 
 function(swift_create_stdlib_targets name variant define_all_alias)

stdlib/public/Darwin/CMakeLists.txt

@@ -5,7 +5,12 @@ if(SWIFT_BUILD_DYNAMIC_SDK_OVERLAY)
   list(APPEND SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES SHARED)
 endif()
 if(SWIFT_BUILD_STATIC_SDK_OVERLAY)
-  list(APPEND SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES STATIC)
+  list_intersect("${SWIFT_APPLE_PLATFORMS}" "${SWIFT_SDKS}" building_darwin_sdks)
+  if(building_darwin_sdks)
+    message(SEND_ERROR "cannot build static standard library for Darwin SDKs")
+  else()
+    list(APPEND SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES STATIC)
+  endif()
 endif()
 
 set(all_overlays