Drop a StringMap.h include, NFC

$ diff -u <(sort thedeps-before.txt) <(sort thedeps-after.txt) \
    | grep '^[-+] ' | sort | uniq -c | sort -nr
    231 -    llvm/include/llvm/ADT/StringMap.h
    171 -    llvm/include/llvm/Support/AllocatorBase.h
    142 -    llvm/include/llvm/Support/PointerLikeTypeTraits.h
diff --git a/llvm/lib/Support/Host.cpp b/llvm/lib/Support/Host.cpp
index 2fb0c25..d7558fa 100644
--- a/llvm/lib/Support/Host.cpp
+++ b/llvm/lib/Support/Host.cpp
@@ -11,9 +11,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/Host.h"
-#include "llvm/Support/TargetParser.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
@@ -21,6 +21,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/TargetParser.h"
 #include "llvm/Support/raw_ostream.h"
 #include <assert.h>
 #include <string.h>