Separate CMake option for "build concurrency lib" and "import concurrency lib"

The CMake option `SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY` was originally
meant to imply that we should build the _Concurrency module, which it still
does. However, to support minimal stdlib builds, it also became a way
to configure the compiler to avoid implicitly importing the
_Concurrency module. However, we build configurations of Swift where
we want the implicit import but don't want to build the _Concurrency
library. Use a new, different option
(`SWIFT_IMPLICIT_CONCURRENCY_IMPORT`) for the "implicit import"
behavior within the compiler, which defaults to "true", and disable
that for minimal stdlib builds.

Fixes rdar://78544947.

Author: DougGregor

CMakeLists.txt

@@ -414,8 +414,12 @@ option(SWIFT_ENABLE_EXPERIMENTAL_DIFFERENTIABLE_PROGRAMMING
   "Enable experimental Swift differentiable programming features"
   FALSE)
 
+option(SWIFT_IMPLICIT_CONCURRENCY_IMPORT
+  "Implicitly import the Swift concurrency module"
+  TRUE)
+
 option(SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
-  "Enable experimental Swift concurrency model"
+  "Enable build of the Swift concurrency module"
   FALSE)
 
 option(SWIFT_ENABLE_DISPATCH

include/swift/Basic/LangOptions.h

@@ -272,7 +272,7 @@ namespace swift {
 
     /// Disable the implicit import of the _Concurrency module.
     bool DisableImplicitConcurrencyModuleImport =
-        !SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY;
+        !SWIFT_IMPLICIT_CONCURRENCY_IMPORT;
 
     /// Should we check the target OSs of serialized modules to see that they're
     /// new enough?

include/swift/Config.h.in

@@ -8,6 +8,6 @@
 
 #cmakedefine HAVE_PROC_PID_RUSAGE 1
 
-#cmakedefine01 SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
+#cmakedefine01 SWIFT_IMPLICIT_CONCURRENCY_IMPORT
 
 #endif // SWIFT_CONFIG_H

utils/build-presets.ini

@@ -2413,7 +2413,7 @@ swift-enable-compatibility-overrides=0
 swift-runtime-macho-no-dyld=1
 swift-stdlib-single-threaded-runtime=1
 swift-stdlib-os-versioning=0
-extra-cmake-options=-DSWIFT_ENABLE_DISPATCH:BOOL=FALSE
+extra-cmake-options=-DSWIFT_ENABLE_DISPATCH:BOOL=FALSE -DSWIFT_IMPLICIT_CONCURRENCY_IMPORT:BOOL=FALSE
 
 [preset: stdlib_S_standalone_minimal_macho_x86_64,build]
 mixin-preset=