[ELF] Fix lld build on Windows/MinGW

The patch in https://reviews.llvm.org/D64077 causes a build failure
because both the Defined and SharedSymbol classes are bigger than 80
bytes on MinGW 8.

This patch fixes this build failure by changing the type of the
bitfields. It is a similar change to the bitfield changes in
https://reviews.llvm.org/D64238, but instead of changing to bool I
decided to use uint8_t because one of the bitfields takes up two bits
instead of one.

Note: the patch is slightly different from the one reviewed in
Phabricator, but it is a trivial change to align it with LLVM master
instead of LLVM 9. Also, it passes all lld tests.

Differential Revision: https://reviews.llvm.org/D70266

lld/ELF/Symbols.h

@@ -105,13 +105,13 @@ public:
 
   // Symbol visibility. This is the computed minimum visibility of all
   // observed non-DSO symbols.
-  unsigned visibility : 2;
+  uint8_t visibility : 2;
 
   // True if the symbol was used for linking and thus need to be added to the
   // output file's symbol table. This is true for all symbols except for
   // unreferenced DSO symbols, lazy (archive) symbols, and bitcode symbols that
   // are unreferenced except by other bitcode objects.
-  unsigned isUsedInRegularObj : 1;
+  uint8_t isUsedInRegularObj : 1;
 
   // Used by a Defined symbol with protected or default visibility, to record
   // whether it is required to be exported into .dynsym. This is set when any of
@@ -121,25 +121,25 @@ public:
   // - If -shared or --export-dynamic is specified, any symbol in an object
   //   file/bitcode sets this property, unless suppressed by LTO
   //   canBeOmittedFromSymbolTable().
-  unsigned exportDynamic : 1;
+  uint8_t exportDynamic : 1;
 
   // True if the symbol is in the --dynamic-list file. A Defined symbol with
   // protected or default visibility with this property is required to be
   // exported into .dynsym.
-  unsigned inDynamicList : 1;
+  uint8_t inDynamicList : 1;
 
   // False if LTO shouldn't inline whatever this symbol points to. If a symbol
   // is overwritten after LTO, LTO shouldn't inline the symbol because it
   // doesn't know the final contents of the symbol.
-  unsigned canInline : 1;
+  uint8_t canInline : 1;
 
   // Used by Undefined and SharedSymbol to track if there has been at least one
   // undefined reference to the symbol. The binding may change to STB_WEAK if
   // the first undefined reference from a non-shared object is weak.
-  unsigned referenced : 1;
+  uint8_t referenced : 1;
 
   // True if this symbol is specified by --trace-symbol option.
-  unsigned traced : 1;
+  uint8_t traced : 1;
 
   inline void replace(const Symbol &newSym);
 
@@ -248,28 +248,28 @@ protected:
 public:
   // True the symbol should point to its PLT entry.
   // For SharedSymbol only.
-  unsigned needsPltAddr : 1;
+  uint8_t needsPltAddr : 1;
 
   // True if this symbol is in the Iplt sub-section of the Plt and the Igot
   // sub-section of the .got.plt or .got.
-  unsigned isInIplt : 1;
+  uint8_t isInIplt : 1;
 
   // True if this symbol needs a GOT entry and its GOT entry is actually in
   // Igot. This will be true only for certain non-preemptible ifuncs.
-  unsigned gotInIgot : 1;
+  uint8_t gotInIgot : 1;
 
   // True if this symbol is preemptible at load time.
-  unsigned isPreemptible : 1;
+  uint8_t isPreemptible : 1;
 
   // True if an undefined or shared symbol is used from a live section.
-  unsigned used : 1;
+  uint8_t used : 1;
 
   // True if a call to this symbol needs to be followed by a restore of the
   // PPC64 toc pointer.
-  unsigned needsTocRestore : 1;
+  uint8_t needsTocRestore : 1;
 
   // True if this symbol is defined by a linker script.
-  unsigned scriptDefined : 1;
+  uint8_t scriptDefined : 1;
 
   // The partition whose dynamic symbol table contains this symbol's definition.
   uint8_t partition = 1;