[llvm] Add support for running tests as root (#75285)

There are a few test that check access permissions, so they need to be
disabled when running the tests as root.

The most common use case for running tests as root is inside of a
container. GitHub Actions, for example, only supports running the root
user inside of containers, so this change is necessary in order to run
the tests inside of a container running in the GitHub Actions
environment.

llvm/test/tools/llvm-ar/error-opening-permission.test

@@ -1,6 +1,7 @@
 ## Unsupported on windows as marking files "unreadable"
 ## is non-trivial on windows.
 # UNSUPPORTED: system-windows
+# REQUIRES: non-root-user
 
 # RUN: rm -rf %t && mkdir -p %t
 # RUN: echo file1 > %t/1.txt

llvm/test/tools/llvm-dwarfdump/X86/output.s

@@ -1,3 +1,4 @@
+# REQUIRES: non-root-user
 # RUN: rm -f %t1.txt %t2.txt %t3.txt
 # RUN: llvm-mc %S/brief.s -filetype obj -triple x86_64-apple-darwin -o %t.o
 

llvm/test/tools/llvm-ifs/fail-file-write.test

@@ -1,6 +1,7 @@
 ## Test failing to write output file on non-windows platforms.
 
 # UNSUPPORTED: system-windows
+# REQUIRES: non-root-user
 # RUN: rm -rf %t.TestDir
 # RUN: mkdir %t.TestDir
 # RUN: touch %t.TestDir/Output.TestFile

llvm/test/tools/llvm-ranlib/error-opening-permission.test

@@ -1,5 +1,6 @@
 ## Unsupported on windows as marking files "unreadable" is non-trivial on windows.
 # UNSUPPORTED: system-windows
+# REQUIRES: non-root-user
 
 # RUN: rm -rf %t && split-file %s %t && cd %t
 # RUN: yaml2obj 1.yaml -o 1.o

llvm/utils/lit/lit/llvm/config.py

@@ -13,6 +13,17 @@
 lit_path_displayed = False
 
 
+def user_is_root():
+    # os.getuid() is not available on all platforms
+    try:
+        if os.getuid() == 0:
+            return True
+    except:
+        pass
+
+    return False
+
+
 class LLVMConfig(object):
     def __init__(self, lit_config, config):
         self.lit_config = lit_config
@@ -154,6 +165,9 @@ def __init__(self, lit_config, config):
             if re.match(r'^ppc64le.*-linux', target_triple):
                 features.add('target=powerpc64le-linux')
 
+        if not user_is_root():
+            features.add("non-root-user")
+
         use_gmalloc = lit_config.params.get("use_gmalloc", None)
         if lit.util.pythonize_bool(use_gmalloc):
             # Allow use of an explicit path for gmalloc library.