…-java on linux and swift 6.1.2 (#9019)

### Explanation:
(cherry picked from commit 16452e1)

Frequent crashes in LLBuildProgressTracker while building swift-java on
linux and swift 6.1.2

This was a race condition because the 
Command is associated with a handle (pointer) that may be reclaimed when
this function finishes.

### Scope:
Minimal, copy variables into locals before accessing them from async
block.

### Issues:
swiftlang/swift-java#314 almost all CI runs
fail with this race condition due to the timing of the command being
influenced by the gradle build in swift-java.

### Original PRs:
#8998

### Risk:
Minimal. Change explicitly copies variables prior to usage in async
block. This avoided a race condition that would manifest before as null
pointer crashes when trying to access these variables.


Change has been tested in main and 6.2

### Testing:
Confirmed fixed in main and 6.2. Manually verified in always reproducing
project.