Revert "[lit] Echo full RUN lines in case of external shells (llvm#65267)"

This reverts commit 19b44c2.

The reason for the revert is discussed at:
https://discourse.llvm.org/t/rfc-improving-lits-debug-output/72839/52

Author: jdenny-ornl

llvm/utils/lit/lit/TestRunner.py

@@ -1153,14 +1153,8 @@ def executeScript(test, litConfig, tmpBase, commands, cwd):
     for j, ln in enumerate(commands):
         match = re.match(kPdbgRegex, ln)
         if match:
-            dbg = match.group(1)
             command = match.group(2)
-            commands[j] = f"echo '{dbg}'"
-            if command:
-                commands[j] += f": {shlex.quote(command.lstrip())} >&2 " \
-                               f"&& {command}"
-            else:
-                commands[j] += " has no command after substitutions >&2"
+            commands[j] = match.expand(": '\\1'; \\2" if command else ": '\\1'")
             if litConfig.per_test_coverage:
                 # Extract the test case name from the test object
                 test_case_name = test.path_in_suite[-1]

llvm/utils/lit/tests/Inputs/shtest-run-at-line/external-shell/empty-run-line.txt

@@ -6,35 +6,23 @@
 # END.
 
 
-# CHECK: Testing: 6 tests
+# CHECK: Testing: 4 tests
 
 
 # In the case of the external shell, we check for only RUN lines in stderr in
 # case some shell implementations format "set -x" output differently.
 
 # CHECK-LABEL: FAIL: shtest-run-at-line :: external-shell/basic.txt
 
-#      CHECK: Command Output (stderr)
-# CHECK-NEXT: --
-#      CHECK: {{^}}RUN: at line 4: true
-#      CHECK: {{^}}RUN: at line 5: false
-#  CHECK-NOT: RUN
-
-# CHECK-LABEL: FAIL: shtest-run-at-line :: external-shell/empty-run-line.txt
-
-#      CHECK: Command Output (stderr)
-# CHECK-NEXT: --
-#      CHECK: {{^}}RUN: at line 2 has no command after substitutions
-#      CHECK: {{^}}RUN: at line 3: false
-#  CHECK-NOT: RUN
+# CHECK:     RUN: at line 4
+# CHECK:     RUN: at line 5
+# CHECK-NOT: RUN
 
 # CHECK-LABEL: FAIL: shtest-run-at-line :: external-shell/line-continuation.txt
 
-#      CHECK: Command Output (stderr)
-# CHECK-NEXT: --
-#      CHECK: {{^}}RUN: at line 4: echo 'foo bar' | FileCheck
-#      CHECK: {{^}}RUN: at line 6: echo 'foo baz' | FileCheck
-#  CHECK-NOT: RUN
+# CHECK:     RUN: at line 4
+# CHECK:     RUN: at line 6
+# CHECK-NOT: RUN
 
 
 # CHECK-LABEL: FAIL: shtest-run-at-line :: internal-shell/basic.txt
@@ -49,16 +37,6 @@
 # CHECK-NEXT: # executed command: false
 # CHECK-NOT:  RUN
 
-# CHECK-LABEL: FAIL: shtest-run-at-line :: internal-shell/empty-run-line.txt
-
-#      CHECK: Command Output (stdout)
-# CHECK-NEXT: --
-# CHECK-NEXT: # RUN: at line 2 has no command after substitutions
-# CHECK-NEXT: # RUN: at line 3
-# CHECK-NEXT: false
-# CHECK-NEXT: # executed command: false
-#  CHECK-NOT: RUN
-
 # CHECK-LABEL: FAIL: shtest-run-at-line :: internal-shell/line-continuation.txt
 
 # CHECK:      Command Output (stdout)