Add -lm to the default libs for Linux & Darwin

libm is a default library for device builds, so default it for host
builds as well.

Also removes duplicate additions of -ldl, -lpthread, -lm and -lrt.

Test: m host
Change-Id: I6a07e12053090eb6997b79d4091c28ac9a9022de

tools/makeparallel/Android.bp

@@ -18,9 +18,4 @@ cc_binary_host {
         "makeparallel.cpp",
     ],
     cflags: ["-Wall", "-Werror"],
-    target: {
-        linux: {
-            host_ldlibs: ["-lrt", "-lpthread"],
-        },
-    },
 }