stubs: clean up android support routines

Some of the previously used stubs are no longer needed in newer releases
of the Android API.  Android L and Android O provide the functions in
their associated versions of bionic.  This is needed to build against a
newer version of the SDK.

Author: compnerd

stdlib/public/stubs/Stubs.cpp

@@ -45,25 +45,28 @@
 #include <sstream>
 #include <cmath>
 #elif defined(__ANDROID__)
-// Android's libc implementation Bionic currently only supports the "C" locale
-// (https://android.googlesource.com/platform/bionic/+/ndk-r11c/libc/bionic/locale.cpp#40).
-// As such, we have no choice but to map functions like strtod_l, which should
-// respect the given locale_t parameter, to functions like strtod, which do not.
 #include <locale.h>
+
+#include <android/api-level.h>
+
+#if __ANDROID_API__ < 21 // Introduced in Android API 21 - L
+static inline long double swift_strtold_l(const char *nptr, char **endptr,
+                                          locale_t) {
+  return strtod(nptr, endptr);
+}
+#define strtold_l swift_strtold_l
+#endif
+
+#if __ANDROID_API__ < 26 // Introduced in Android API 26 - O
 static double swift_strtod_l(const char *nptr, char **endptr, locale_t loc) {
   return strtod(nptr, endptr);
 }
 static float swift_strtof_l(const char *nptr, char **endptr, locale_t loc) {
   return strtof(nptr, endptr);
 }
-static long double swift_strtold_l(const char *nptr,
-                                   char **endptr,
-                                   locale_t loc) {
-  return strtod(nptr, endptr);
-}
 #define strtod_l swift_strtod_l
 #define strtof_l swift_strtof_l
-#define strtold_l swift_strtold_l
+#endif
 #elif defined(__linux__)
 #include <locale.h>
 #else