Add IsRunningWithVFS1 to test util

VFS2 is adding more functionality than VFS1. In order to test
new functionality, it's required to skip some tests with VFS1.
To skip tests, use:

SKIP_IF(IsRunningWithVFS1());

The test will run in Linux and gVisor with VFS2 enabled.

Updates #1035

PiperOrigin-RevId: 312698616

test/util/test_util.cc

@@ -42,12 +42,13 @@ namespace testing {
 
 #define TEST_ON_GVISOR "TEST_ON_GVISOR"
 #define GVISOR_NETWORK "GVISOR_NETWORK"
+#define GVISOR_VFS "GVISOR_VFS"
 
 bool IsRunningOnGvisor() { return GvisorPlatform() != Platform::kNative; }
 
 const std::string GvisorPlatform() {
   // Set by runner.go.
-  char* env = getenv(TEST_ON_GVISOR);
+  const char* env = getenv(TEST_ON_GVISOR);
   if (!env) {
     return Platform::kNative;
   }
@@ -55,10 +56,19 @@ const std::string GvisorPlatform() {
 }
 
 bool IsRunningWithHostinet() {
-  char* env = getenv(GVISOR_NETWORK);
+  const char* env = getenv(GVISOR_NETWORK);
   return env && strcmp(env, "host") == 0;
 }
 
+bool IsRunningWithVFS1() {
+  const char* env = getenv(GVISOR_VFS);
+  if (env == nullptr) {
+    // If not set, it's running on Linux.
+    return false;
+  }
+  return strcmp(env, "VFS1") == 0;
+}
+
 // Inline cpuid instruction.  Preserve %ebx/%rbx register. In PIC compilations
 // %ebx contains the address of the global offset table. %rbx is occasionally
 // used to address stack variables in presence of dynamic allocas.

test/util/test_util.h

@@ -220,6 +220,7 @@ constexpr char kKVM[] = "kvm";
 bool IsRunningOnGvisor();
 const std::string GvisorPlatform();
 bool IsRunningWithHostinet();
+bool IsRunningWithVFS1();
 
 #ifdef __linux__
 void SetupGvisorDeathTest();