[lldb] Fix flakyness in Minidump/no-process-id.yaml

(cherry picked from commit 8e893df)

Author: JDevlieghere

lldb/test/Shell/Minidump/no-process-id.yaml

@@ -1,8 +1,7 @@
 # RUN: yaml2obj %s -o %t
-# RUN: %lldb -c %t -o "thread list" -o "register read" -b 2>&1 | FileCheck %s
+# RUN: %lldb -c %t -o "thread list" -o "register read" -b 2> %t.stderr | FileCheck %s
 
 # CHECK: (lldb) target create --core
-# CHECK: unable to retrieve process ID from minidump file, setting process ID to 1
 # CHECK: Core file {{.*}} was loaded.
 
 # CHECK: (lldb) thread list
@@ -12,6 +11,9 @@
 # CHECK: (lldb) register read
 # CHECK: rsp = 0x00007ffceb34a210
 
+# RUN: cat %t.stderr | FileCheck %s --check-prefix ERROR
+# ERROR: unable to retrieve process ID from minidump file, setting process ID to 1
+
 --- !minidump
 Streams:
   - Type:            ThreadList