fixup! Initialize Process to &Invalid instead of nullptr, so an additional bool is not needed

also fix platform .inc files

Author: jeremyd2019

llvm/lib/Support/Unix/DynamicLibrary.inc

@@ -17,7 +17,7 @@ DynamicLibrary::HandleSet::~HandleSet() {
   // Close the libraries in reverse order.
   for (void *Handle : llvm::reverse(Handles))
     ::dlclose(Handle);
-  if (Process)
+  if (Process != &Invalid)
     ::dlclose(Process);
 
   // llvm_shutdown called, Return to default

llvm/lib/Support/Windows/DynamicLibrary.inc

@@ -26,7 +26,7 @@ DynamicLibrary::HandleSet::~HandleSet() {
     FreeLibrary(HMODULE(Handle));
 
   // 'Process' should not be released on Windows.
-  assert((!Process || Process == this) && "Bad Handle");
+  assert((Process == &Invalid || Process == this) && "Bad Handle");
   // llvm_shutdown called, Return to default
   DynamicLibrary::SearchOrder = DynamicLibrary::SO_Linker;
 }
@@ -60,7 +60,7 @@ static DynamicLibrary::HandleSet *IsOpenedHandlesInstance(void *Handle) {
 
 void DynamicLibrary::HandleSet::DLClose(void *Handle) {
   if (HandleSet *HS = IsOpenedHandlesInstance(Handle))
-    HS->Process = nullptr; // Just drop the *Process* handle.
+    HS->Process = &Invalid; // Just drop the *Process* handle.
   else
     FreeLibrary((HMODULE)Handle);
 }
@@ -89,7 +89,7 @@ void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
     return (void *)uintptr_t(GetProcAddress((HMODULE)Handle, Symbol));
 
   // Could have done a dlclose on the *Process* handle
-  if (!HS->Process)
+  if (HS->Process == &Invalid)
     return nullptr;
 
   // Trials indicate EnumProcessModulesEx is consistantly faster than using