Prevent HostInfoBase::GetAugmentedArchSpec() from attaching "unknown" environments

[aprantl]

Summary

Messy stuff. Environments are optional and a missing environment is distinct from the default "unknown" environment enumerator.
Also the test sucks, because the function uses the host triple and is unpredictable.

rdar://91007207

[JDevlieghere]

Fun stuff.

lldb/source/Host/common/HostInfoBase.cpp

if (auto kind = HostInfo::ParseArchitectureKind(triple))
     return HostInfo::GetArchitecture(*kind);
 
   llvm::Triple host_triple(llvm::sys::getDefaultTargetTriple());
 
   if (normalized_triple.getVendorName().empty())
     normalized_triple.setVendor(host_triple.getVendor());
   if (normalized_triple.getOSName().empty())
     normalized_triple.setOS(host_triple.getOS());
-  if (normalized_triple.getEnvironmentName().empty())
+  if (normalized_triple.getEnvironmentName().empty() &&
+      !host_triple.getEnvironmentName().empty())
     normalized_triple.setEnvironment(host_triple.getEnvironment());
   return ArchSpec(normalized_triple);
 }
 
 bool HostInfoBase::ComputePathRelativeToLibrary(FileSpec &file_spec,
                                                 llvm::StringRef dir) {
   Log *log = GetLog(LLDBLog::Host);
 

lldb/unittests/Host/HostInfoTest.cpp

TEST_F(HostInfoTest, GetAugmentedArchSpec) {
   EXPECT_EQ(spec.GetTriple().getArch(), Triple::x86_64);
   EXPECT_EQ(spec.GetTriple().getOS(), triple.getOS());
   EXPECT_EQ(spec.GetTriple().getVendor(), triple.getVendor());
   EXPECT_EQ(spec.GetTriple().getEnvironment(), triple.getEnvironment());
 
   // Test LLDB_ARCH_DEFAULT
   EXPECT_EQ(HostInfo::GetAugmentedArchSpec(LLDB_ARCH_DEFAULT).GetTriple(),
             HostInfo::GetArchitecture(HostInfo::eArchKindDefault).GetTriple());
+  EXPECT_NE(
+      HostInfo::GetAugmentedArchSpec("armv7k").GetTriple().getEnvironmentName(),
+      "unknown");
 }
 
 TEST_F(HostInfoTest, GetHostname) {
   // Check non-empty string input works correctly.
   std::string s("abc");
   EXPECT_TRUE(HostInfo::GetHostname(s));
 }