Attempt to reduce the number of embedded stdlib targets being built simultaneously.

We are seeing strange crashes during embedded stdlib build stage on Ubuntu 24.04. These crashes only seem to occur when we dispatch many stdlib emit-module tasks at the same time. While we root-cause it, this change attempts to slow down the process to only two Embedded StdLib tasks at-a-time.

Workaround for rdar://137674862

Author: artemcm

stdlib/public/Platform/CMakeLists.txt

@@ -83,6 +83,8 @@ if(SWIFT_SHOULD_BUILD_EMBEDDED_STDLIB)
 
   add_custom_target(embedded-darwin)
   add_dependencies(embedded-libraries embedded-darwin)
+
+  set_property(GLOBAL APPEND PROPERTY JOB_POOLS one_job=1)
   foreach(entry ${EMBEDDED_STDLIB_TARGET_TRIPLES})
     string(REGEX REPLACE "[ \t]+" ";" list "${entry}")
     list(GET list 0 arch)
@@ -125,6 +127,7 @@ if(SWIFT_SHOULD_BUILD_EMBEDDED_STDLIB)
       INSTALL_IN_COMPONENT stdlib
       )
     add_dependencies(embedded-darwin embedded-darwin-${mod})
+    set_property(TARGET embedded-darwin-${mod} PROPERTY JOB_POOL_COMPILE one_job)
   endforeach()
 endif()