[lit] Split Linux specific ulimit tests

Some of the ulimit limits do not work on some POSIX platforms. THe
motivating example here is ulimit -v on MacOS as the relevant system
calls are not implemented in XNU. Splitting the tests lets us keep test
coverage on POSIX (non-Linux) platforms.

Author: boomanaiden154

llvm/utils/lit/tests/Inputs/shtest-ulimit-linux/lit.cfg

@@ -0,0 +1,8 @@
+import lit.formats
+
+config.name = "shtest-ulimit"
+config.suffixes = [".txt"]
+config.test_format = lit.formats.ShTest(execute_external=False)
+config.test_source_root = None
+config.test_exec_root = None
+config.substitutions.append(("%{python}", '"%s"' % (sys.executable)))

llvm/utils/lit/tests/Inputs/shtest-ulimit-linux/ulimit_okay.txt

@@ -0,0 +1,4 @@
+# RUN: ulimit -v 1048576
+# RUN: %{python} %S/../shtest-ulimit/print_limits.py
+# Fail the test so that we can assert on the output.
+# RUN: not echo return

llvm/utils/lit/tests/Inputs/shtest-ulimit/ulimit_okay.txt

@@ -1,4 +1,3 @@
-# RUN: ulimit -v 1048576
 # RUN: ulimit -n 50
 # RUN: %{python} %S/print_limits.py
 # Fail the test so that we can assert on the output.

llvm/utils/lit/tests/shtest-ulimit.py

@@ -3,13 +3,8 @@
 # ulimit does not work on non-POSIX platforms.
 # UNSUPPORTED: system-windows
 
-# TODO(boomanaiden154): The test fails on some non-Linux POSIX
-# platforms (like MacOS) due to the underlying system not supporting
-# ulimit -v. This test needs to be carved up so we keep full test
-# coverage on Linux and as much as possible on other platforms.
-# REQUIRES: system-linux
-
 # RUN: not %{lit} -a -v %{inputs}/shtest-ulimit | FileCheck %s
+# RUN: %if system-linux %{ not %{lit} -a -v %{inputs}/shtest-ulimit-linux | FileCheck %s --check-prefix CHECK-LINUX %}
 
 # CHECK: -- Testing: 2 tests{{.*}}
 
@@ -18,7 +13,11 @@
 # CHECK: 'ulimit' requires two arguments
 
 # CHECK-LABEL: FAIL: shtest-ulimit :: ulimit_okay.txt ({{[^)]*}})
-# CHECK: ulimit -v 1048576
 # CHECK: ulimit -n 50
-# CHECK: RLIMIT_AS=1073741824
 # CHECK: RLIMIT_NOFILE=50
+
+# CHECK-LINUX: -- Testing: 1 tests{{.*}}
+
+# CHECK-LINUX-LABEL: FAIL: shtest-ulimit :: ulimit_okay.txt ({{[^)]*}})
+# CHECK-LINUX: ulimit -v 1048576
+# CHECK-LINUX: RLIMIT_AS=1073741824