[lld-macho] Have all load commands aligned to the word size

[int3]

Summary

This is what ld64 does, and also what we already do for most of the
other load commands. I'm not aware of a good way to test this, but I
don't think it really matters.

lld/MachO/Writer.cpp

public:
   LCDylib(LoadCommandType type, StringRef path,
           uint32_t compatibilityVersion = 0, uint32_t currentVersion = 0)
       : type(type), path(path), compatibilityVersion(compatibilityVersion),
         currentVersion(currentVersion) {
     instanceCount++;
   }
 
   uint32_t getSize() const override {
-    return alignTo(sizeof(dylib_command) + path.size() + 1, 8);
+    return alignToPowerOf2(sizeof(dylib_command) + path.size() + 1,
+                           target->wordSize);
   }
 
   void writeTo(uint8_t *buf) const override {
     auto *c = reinterpret_cast<dylib_command *>(buf);
     buf += sizeof(dylib_command);
 
     c->cmd = type;
     c->cmdsize = getSize();
private:
   static uint32_t instanceCount;
 };
 
 uint32_t LCDylib::instanceCount = 0;
 
 class LCLoadDylinker final : public LoadCommand {
 public:
   uint32_t getSize() const override {
-    return alignTo(sizeof(dylinker_command) + path.size() + 1, 8);
+    return alignToPowerOf2(sizeof(dylinker_command) + path.size() + 1,
+                           target->wordSize);
   }
 
   void writeTo(uint8_t *buf) const override {
     auto *c = reinterpret_cast<dylinker_command *>(buf);
     buf += sizeof(dylinker_command);
 
     c->cmd = LC_LOAD_DYLINKER;
     c->cmdsize = getSize();