[openmp] Allow to re-run tests

When packaging LLVM we've seen arbitrary tests failing. It happened
sporadically and most of the times the test do work if they are run a
second time on the next day.

The tests themselves were always different and we didn't know ahead
of time which ones we wanted to re-run. That's we
[filter-out](https://src.fedoraproject.org/rpms/llvm/blob/rawhide/f/llvm.spec#_2326)
a lot of `libomp` and `libarcher` tests.

This changes allows us to set `LIT_OPTS="-Dmaximum_retries_per_test=12"`
when running the "check-openmp" build target. Then any test in the `openmp`
directory will at most be re-run 12 times. 12 is just an example here and
it is up to the caller of the build target to define this.

Please note, that only adds the possibility to re-run openmp tests. It
does not actually do it until the caller specifies
`-Dmaximum_retries_per_test=<INT>` either on a call to `lit` or in
`LIT_OPTS`.

Downstream ticket: https://issues.redhat.com/browse/LLVM-145

Author: kwk

openmp/libompd/test/lit.cfg

@@ -81,3 +81,7 @@ config.substitutions.append(("%ompt-tool",
 
 config.substitutions.append(("FileCheck", config.test_filecheck))
 
+maximum_retries_per_test = lit_config.params.get("maximum_retries_per_test", None)
+if maximum_retries_per_test is not None:
+    config.test_retry_attempts = int(maximum_retries_per_test)
+

openmp/runtime/test/lit.cfg

@@ -226,3 +226,7 @@ if config.has_ompt:
         config.substitutions.append(("%no-as-needed-flag", "-Wl,--no-as-needed"))
 else:
     config.substitutions.append(("FileCheck", config.test_filecheck))
+
+maximum_retries_per_test = lit_config.params.get("maximum_retries_per_test", None)
+if maximum_retries_per_test is not None:
+    config.test_retry_attempts = int(maximum_retries_per_test)

openmp/tools/archer/tests/lit.cfg

@@ -138,3 +138,7 @@ elif config.operating_system == 'Darwin':
     config.substitutions.append(("%preload-tool", "env DYLD_INSERT_LIBRARIES=%T/tool.so"))
 else:
     config.substitutions.append(("%preload-tool", "env LD_PRELOAD=%T/tool.so"))
+
+maximum_retries_per_test = lit_config.params.get("maximum_retries_per_test", None)
+if maximum_retries_per_test is not None:
+    config.test_retry_attempts = int(maximum_retries_per_test)

openmp/tools/multiplex/tests/lit.cfg

@@ -103,3 +103,6 @@ config.substitutions.append(("%clang", config.test_c_compiler))
 config.substitutions.append(("%openmp_flag", config.test_openmp_flags))
 config.substitutions.append(("%cflags", config.test_flags))
 
+maximum_retries_per_test = lit_config.params.get("maximum_retries_per_test", None)
+if maximum_retries_per_test is not None:
+    config.test_retry_attempts = int(maximum_retries_per_test)