Update CI to use Android NDK r25b

This commit updates the CI definitions to use the most recent Android
LTS NDK release: r25b.  Changes since the last NDK used by Rust negate
the need to generate "standalone toolchains" and newer NDKs can be used
in-place.

See https://developer.android.com/ndk/guides/other_build_systems#overview

src/bootstrap/cc_detect.rs

@@ -47,6 +47,8 @@ fn cc2ar(cc: &Path, target: TargetSelection) -> Option<PathBuf> {
         Some(PathBuf::from("ar"))
     } else if target.contains("vxworks") {
         Some(PathBuf::from("wr-ar"))
+    } else if target.contains("android") {
+        Some(cc.parent().unwrap().join(PathBuf::from("llvm-ar")))
     } else {
         let parent = cc.parent().unwrap();
         let file = cc.file_name().unwrap().to_str().unwrap();
@@ -166,13 +168,22 @@ fn set_compiler(
         // compiler already takes into account the triple in question.
         t if t.contains("android") => {
             if let Some(ndk) = config.and_then(|c| c.ndk.as_ref()) {
-                let target = target
-                    .triple
-                    .replace("armv7neon", "arm")
-                    .replace("armv7", "arm")
-                    .replace("thumbv7neon", "arm")
-                    .replace("thumbv7", "arm");
-                let compiler = format!("{}-{}", target, compiler.clang());
+                let mut triple_iter = target.triple.split("-");
+                let triple_translated = if let Some(arch) = triple_iter.next() {
+                    let arch_new = match arch {
+                        "arm" | "armv7" | "armv7neon" | "thumbv7" | "thumbv7neon" => "armv7a",
+                        other => other,
+                    };
+                    std::iter::once(arch_new).chain(triple_iter).collect::<Vec<&str>>().join("-")
+                } else {
+                    target.triple.to_string()
+                };
+
+                // API 19 is the earliest API level supported by NDK r25b but AArch64 and x86_64 support
+                // begins at API level 21.
+                let api_level =
+                    if t.contains("aarch64") || t.contains("x86_64") { "21" } else { "19" };
+                let compiler = format!("{}{}-{}", triple_translated, api_level, compiler.clang());
                 cfg.compiler(ndk.join("bin").join(compiler));
             }
         }

src/ci/docker/host-x86_64/arm-android/Dockerfile

@@ -6,7 +6,7 @@ RUN sh /scripts/android-base-apt-get.sh
 
 COPY scripts/android-ndk.sh /scripts/
 RUN . /scripts/android-ndk.sh && \
-    download_and_make_toolchain android-ndk-r15c-linux-x86_64.zip arm 14
+    download_ndk android-ndk-r25b-linux.zip
 
 RUN dpkg --add-architecture i386 && \
     apt-get update && \
@@ -30,7 +30,7 @@ ENV PATH=$PATH:/android/sdk/platform-tools
 
 ENV TARGETS=arm-linux-androideabi
 
-ENV RUST_CONFIGURE_ARGS --arm-linux-androideabi-ndk=/android/ndk/arm-14
+ENV RUST_CONFIGURE_ARGS --arm-linux-androideabi-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/
 
 ENV SCRIPT python3 ../x.py --stage 2 test --host='' --target $TARGETS
 

src/ci/docker/host-x86_64/dist-android/Dockerfile

@@ -6,14 +6,7 @@ RUN sh /scripts/android-base-apt-get.sh
 # ndk
 COPY scripts/android-ndk.sh /scripts/
 RUN . /scripts/android-ndk.sh && \
-    download_ndk android-ndk-r15c-linux-x86_64.zip && \
-    make_standalone_toolchain arm 14 && \
-    make_standalone_toolchain x86 14 && \
-    make_standalone_toolchain arm 21 && \
-    make_standalone_toolchain x86 21 && \
-    make_standalone_toolchain arm64 21 && \
-    make_standalone_toolchain x86_64 21 && \
-    remove_ndk
+    download_ndk android-ndk-r25b-linux.zip
 
 # env
 ENV TARGETS=arm-linux-androideabi
@@ -26,12 +19,12 @@ ENV TARGETS=$TARGETS,x86_64-linux-android
 ENV RUST_CONFIGURE_ARGS \
       --enable-extended \
       --enable-profiler \
-      --arm-linux-androideabi-ndk=/android/ndk/arm-14 \
-      --armv7-linux-androideabi-ndk=/android/ndk/arm-14 \
-      --thumbv7neon-linux-androideabi-ndk=/android/ndk/arm-14 \
-      --i686-linux-android-ndk=/android/ndk/x86-14 \
-      --aarch64-linux-android-ndk=/android/ndk/arm64-21 \
-      --x86_64-linux-android-ndk=/android/ndk/x86_64-21 \
+      --arm-linux-androideabi-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/ \
+      --armv7-linux-androideabi-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/ \
+      --thumbv7neon-linux-androideabi-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/ \
+      --i686-linux-android-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/ \
+      --aarch64-linux-android-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/ \
+      --x86_64-linux-android-ndk=/android/ndk/toolchains/llvm/prebuilt/linux-x86_64/ \
       --disable-docs
 
 ENV SCRIPT python3 ../x.py dist --host='' --target $TARGETS

src/ci/docker/scripts/android-ndk.sh

@@ -4,28 +4,10 @@ set -ex
 URL=https://dl.google.com/android/repository
 
 download_ndk() {
-    mkdir -p /android/ndk
-    cd /android/ndk
+    mkdir /android/
+    cd /android
     curl -fO $URL/$1
     unzip -q $1
     rm $1
     mv android-ndk-* ndk
 }
-
-make_standalone_toolchain() {
-    # See https://developer.android.com/ndk/guides/standalone_toolchain.htm
-    python3 /android/ndk/ndk/build/tools/make_standalone_toolchain.py \
-        --install-dir /android/ndk/$1-$2 \
-        --arch $1 \
-        --api $2
-}
-
-remove_ndk() {
-    rm -rf /android/ndk/ndk
-}
-
-download_and_make_toolchain() {
-    download_ndk $1 && \
-    make_standalone_toolchain $2 $3 && \
-    remove_ndk
-}