[MSVC] Use the correct casing of HostX64/HostX86

[mstorsjo]

Summary

If accessing the MSVC installation root directly on a case sensitive filesystem, these details matter.

[hans]

Looks good to me.

cfe/trunk/lib/Driver/ToolChains/MSVC.cpp

if (Linker.equals_lower("link")) {
     if (!TC.FoundMSVCInstall() && !llvm::sys::fs::can_execute(linkPath))
       C.getDriver().Diag(clang::diag::warn_drv_msvc_not_found);
 
 #ifdef _WIN32
     // When cross-compiling with VS2017 or newer, link.exe expects to have
     // its containing bin directory at the top of PATH, followed by the
     // native target bin directory.
     // e.g. when compiling for x86 on an x64 host, PATH should start with:
-    // /bin/HostX64/x86;/bin/HostX64/x64
+    // /bin/Hostx64/x86;/bin/Hostx64/x64
     // This doesn't attempt to handle ToolsetLayout::DevDivInternal.
     if (TC.getIsVS2017OrNewer() &&
         llvm::Triple(llvm::sys::getProcessTriple()).getArch() != TC.getArch()) {
       auto HostArch = llvm::Triple(llvm::sys::getProcessTriple()).getArch();
 
       auto EnvBlockWide =
           std::unique_ptr<wchar_t[], decltype(&FreeEnvironmentStringsW)>(
               GetEnvironmentStringsW(), FreeEnvironmentStringsW);
MSVCToolChain::getSubDirectoryPath(SubDirectoryType Type,
   }
 
   llvm::SmallString<256> Path(VCToolChainPath);
   switch (Type) {
   case SubDirectoryType::Bin:
     if (VSLayout == ToolsetLayout::VS2017OrNewer) {
       const bool HostIsX64 =
           llvm::Triple(llvm::sys::getProcessTriple()).isArch64Bit();
-      const char *const HostName = HostIsX64 ? "HostX64" : "HostX86";
+      const char *const HostName = HostIsX64 ? "Hostx64" : "Hostx86";
       llvm::sys::path::append(Path, "bin", HostName, SubdirName);
     } else { // OlderVS or DevDivInternal
       llvm::sys::path::append(Path, "bin", SubdirName);
     }
     break;
   case SubDirectoryType::Include:
     llvm::sys::path::append(Path, IncludeName);
     break;