libretro: reenable android build (#1124)

Author: warmenhoven

.gitlab-ci.yml

@@ -100,22 +100,28 @@ libretro-build-osx-arm64:
 
 ################################### CELLULAR #################################
 # Android ARMv7a
-# android-armeabi-v7a:
-#   extends:
-#     - .libretro-android-jni-armeabi-v7a
-#     - .core-defs
+android-armeabi-v7a:
+  extends:
+    - .libretro-android-jni-armeabi-v7a
+    - .core-defs
+  variables:
+    NDK_ROOT: /android-sdk-linux/ndk/26.2.11394342
 
 # Android ARMv8a
-# android-arm64-v8a:
-#   extends:
-#     - .libretro-android-jni-arm64-v8a
-#     - .core-defs
+android-arm64-v8a:
+  extends:
+    - .libretro-android-jni-arm64-v8a
+    - .core-defs
+  variables:
+    NDK_ROOT: /android-sdk-linux/ndk/26.2.11394342
 
 # Android 64-bit x86
-# android-x86_64:
-#   extends:
-#     - .libretro-android-jni-x86_64
-#     - .core-defs
+android-x86_64:
+  extends:
+    - .libretro-android-jni-x86_64
+    - .core-defs
+  variables:
+    NDK_ROOT: /android-sdk-linux/ndk/26.2.11394342
 
 # iOS
 libretro-build-ios-arm64:

src/common/bspf.hxx

@@ -70,9 +70,23 @@ using std::istream;
 using std::ostream;
 using std::fstream;
 using std::iostream;
-using std::ostringstream;
 using std::istringstream;
+// Android NDK 26 libc++ lacks ostringstream::view() (C++20 P0408R7)
+#if defined(__ANDROID__) && !defined(__cpp_lib_sstream_from_string_view)
+class ostringstream : public std::ostringstream {
+public:
+  using std::ostringstream::ostringstream;
+  std::string view() const { return str(); }
+};
+class stringstream : public std::stringstream {
+public:
+  using std::stringstream::stringstream;
+  std::string view() const { return str(); }
+};
+#else
+using std::ostringstream;
 using std::stringstream;
+#endif
 using std::unique_ptr;
 using std::shared_ptr;
 using std::make_unique;