[NFC] Inclusive language: rename master flag to main flag

[quinnp]

Summary

[NFC] As part of using inclusive language within the llvm project, this patch
renames master flag to main flag in these comments.

clang/lib/Driver/ToolChains/Clang.cpp

if (!Triple.isMacOSX())
     return false;
 
   return (!Triple.isMacOSXVersionLT(10, 5) &&
           (Triple.getArch() == llvm::Triple::x86_64 ||
            Triple.getArch() == llvm::Triple::arm));
 }
 
 /// Adds exception related arguments to the driver command arguments. There's a
-/// master flag, -fexceptions and also language specific flags to enable/disable
+/// main flag, -fexceptions and also language specific flags to enable/disable
 /// C++ and Objective-C exceptions. This makes it possible to for example
 /// disable C++ exceptions but enable Objective-C exceptions.
 static bool addExceptionArgs(const ArgList &Args, types::ID InputType,
                              const ToolChain &TC, bool KernelOrKext,
                              const ObjCRuntime &objcRuntime,
                              ArgStringList &CmdArgs) {
   const llvm::Triple &Triple = TC.getTriple();
 

llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

if (X86AlignBranchWithin32BBoundaries) {
       // jumps, and (unfused) conditional jumps with nops.  Both the
       // instructions aligned and the alignment method (nop vs prefix) may
       // change in the future.
       AlignBoundary = assumeAligned(32);;
       AlignBranchType.addKind(X86::AlignBranchFused);
       AlignBranchType.addKind(X86::AlignBranchJcc);
       AlignBranchType.addKind(X86::AlignBranchJmp);
     }
-    // Allow overriding defaults set by master flag
+    // Allow overriding defaults set by main flag
     if (X86AlignBranchBoundary.getNumOccurrences())
       AlignBoundary = assumeAligned(X86AlignBranchBoundary);
     if (X86AlignBranch.getNumOccurrences())
       AlignBranchType = X86AlignBranchKindLoc;
     if (X86PadMaxPrefixSize.getNumOccurrences())
       TargetPrefixMax = X86PadMaxPrefixSize;
   }