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: I8f7e799d48a1f427e48dcfb1d0ccba93c5f9780b

cc/linker.go

@@ -211,11 +211,12 @@ func (linker *baseLinker) linkerFlags(ctx ModuleContext, flags Flags) Flags {
 			flags.LdFlags = append(flags.LdFlags, linker.Properties.Host_ldlibs...)
 
 			if !ctx.Windows() {
-				// Add -ldl, -lpthread and -lrt to host builds to match the default behavior of device
+				// Add -ldl, -lpthread, -lm and -lrt to host builds to match the default behavior of device
 				// builds
 				flags.LdFlags = append(flags.LdFlags,
 					"-ldl",
 					"-lpthread",
+					"-lm",
 				)
 				if !ctx.Darwin() {
 					flags.LdFlags = append(flags.LdFlags, "-lrt")

cc/sanitize.go

@@ -330,7 +330,6 @@ func (sanitize *sanitize) flags(ctx ModuleContext, flags Flags) Flags {
 		if ctx.Host() {
 			// -nodefaultlibs (provided with libc++) prevents the driver from linking
 			// libraries needed with -fsanitize=address. http://b/18650275 (WAI)
-			flags.LdFlags = append(flags.LdFlags, "-lm", "-lpthread")
 			flags.LdFlags = append(flags.LdFlags, "-Wl,--no-as-needed")
 		} else {
 			flags.CFlags = append(flags.CFlags, "-mllvm", "-asan-globals=0")
@@ -387,10 +386,6 @@ func (sanitize *sanitize) flags(ctx ModuleContext, flags Flags) Flags {
 		if ctx.Host() {
 			flags.CFlags = append(flags.CFlags, "-fno-sanitize-recover=all")
 			flags.LdFlags = append(flags.LdFlags, sanitizeArg)
-			if ctx.Os() == android.Linux {
-				flags.LdFlags = append(flags.LdFlags, "-lrt")
-			}
-			flags.LdFlags = append(flags.LdFlags, "-ldl")
 			// Host sanitizers only link symbols in the final executable, so
 			// there will always be undefined symbols in intermediate libraries.
 			_, flags.LdFlags = removeFromList("-Wl,--no-undefined", flags.LdFlags)

cc/stl.go

@@ -134,7 +134,6 @@ func (stl *stl) flags(ctx ModuleContext, flags Flags) Flags {
 		if !ctx.toolchain().Bionic() {
 			flags.CppFlags = append(flags.CppFlags, "-nostdinc++")
 			flags.LdFlags = append(flags.LdFlags, "-nodefaultlibs")
-			flags.LdFlags = append(flags.LdFlags, "-lpthread", "-lm")
 			if ctx.staticBinary() {
 				flags.LdFlags = append(flags.LdFlags, hostStaticGccLibs[ctx.Os()]...)
 			} else {

cc/test.go

@@ -145,10 +145,8 @@ func (test *testDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags {
 			flags.CFlags = append(flags.CFlags, "-DGTEST_OS_WINDOWS")
 		case android.Linux:
 			flags.CFlags = append(flags.CFlags, "-DGTEST_OS_LINUX")
-			flags.LdFlags = append(flags.LdFlags, "-lpthread")
 		case android.Darwin:
 			flags.CFlags = append(flags.CFlags, "-DGTEST_OS_MAC")
-			flags.LdFlags = append(flags.LdFlags, "-lpthread")
 		}
 	} else {
 		flags.CFlags = append(flags.CFlags, "-DGTEST_OS_LINUX_ANDROID")