Add libwinpthread, link it into win32 binaries.

Bug: http://b/31665213
Test: wine adb.exe
Test: wine fastboot.exe
Change-Id: I6d6ff69f0c016e2654119a09161685841cbccc7e

Android.bp

@@ -245,6 +245,17 @@ toolchain_library {
     },
 }
 
+toolchain_library {
+    name: "libwinpthread",
+    host_supported: true,
+    enabled: false,
+    target: {
+        windows: {
+            enabled: true
+        },
+    },
+}
+
 toolchain_library {
     name: "libgcov",
     defaults: ["linux_bionic_supported"],

cc/linker.go

@@ -156,6 +156,10 @@ func (linker *baseLinker) linkerDeps(ctx BaseModuleContext, deps Deps) Deps {
 		}
 	}
 
+	if ctx.Os() == android.Windows {
+		deps.LateStaticLibs = append(deps.LateStaticLibs, "libwinpthread")
+	}
+
 	return deps
 }