Android support (swift-server#799)

This PR adds support for Android, mostly just by importing the Android
module when needed.

Author: marcprux

Sources/AsyncHTTPClient/ConnectionPool.swift

@@ -20,7 +20,9 @@ import NIOSSL
 import Darwin.C
 #elseif canImport(Musl)
 import Musl
-#elseif os(Linux) || os(FreeBSD) || os(Android)
+#elseif canImport(Android)
+import Android
+#elseif os(Linux) || os(FreeBSD)
 import Glibc
 #else
 #error("unsupported target operating system")

Sources/AsyncHTTPClient/ConnectionPool/State Machine/HTTPConnectionPool+Backoff.swift

@@ -18,6 +18,8 @@ import NIOCore
 import func Darwin.pow
 #elseif canImport(Musl)
 import func Musl.pow
+#elseif canImport(Android)
+import func Android.pow
 #else
 import func Glibc.pow
 #endif

Sources/AsyncHTTPClient/HTTPClient+HTTPCookie.swift

@@ -26,6 +26,8 @@ import locale_h
 import Darwin
 #elseif canImport(Musl)
 import Musl
+#elseif canImport(Android)
+import Android
 #elseif canImport(Glibc)
 import Glibc
 #endif

Sources/CAsyncHTTPClient/CAsyncHTTPClient.c

@@ -31,7 +31,7 @@ bool swiftahc_cshims_strptime(const char * string, const char * format, struct t
 
 bool swiftahc_cshims_strptime_l(const char * string, const char * format, struct tm * result, void * locale) {
     // The pointer cast is fine as long we make sure it really points to a locale_t.
-#ifdef __musl__
+#if defined(__musl__) || defined(__ANDROID__)
     const char * firstNonProcessed = strptime(string, format, result);
 #else
     const char * firstNonProcessed = strptime_l(string, format, result, (locale_t)locale);

Tests/AsyncHTTPClientTests/HTTPClientTestUtils.swift

@@ -39,6 +39,8 @@ import locale_h
 import Darwin
 #elseif canImport(Musl)
 import Musl
+#elseif canImport(Android)
+import Android
 #elseif canImport(Glibc)
 import Glibc
 #endif