[Linux][Test] Use import-static-libdispatch not import-libdispatch.

We want the static version of Dispatch here.  If we don't use that version,
we'll fail the tests on the release branches (but strangely not on main
for some reason).

rdar://115774613

Author: al45tair

test/Backtracing/CrashStatic.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-build-swift %s -parse-as-library %import-libdispatch -Onone -static-stdlib -g -o %t/CrashStatic
+// RUN: %target-build-swift %s -parse-as-library %import-static-libdispatch -Onone -static-stdlib -g -o %t/CrashStatic
 // RUN: %target-codesign %t/CrashStatic
 // RUN: (env SWIFT_BACKTRACE=enable=yes,cache=no,swift-backtrace=%backtracer %target-run %t/CrashStatic 2>&1 || true) | %FileCheck %s