Update Android target to use new build system integration

config.toml.example

@@ -334,6 +334,18 @@ changelog-seen = 2
 # this is not intended to be used during local development.
 #metrics = false
 
+# When targeting Android, specify the location of the Android NDK. This variable
+# needs to be set to the location of the LLVM toolchain subdirectory within
+# the NDK, found under "toolchains/llvm/prebuilt/<host os>-<host arch>".
+#
+# This option is only compatible with Android NDK r19 or newer. If you are using
+# an older NDK, you will need to create a standalone toolchain and specify the
+# path via the target-specific android-ndk option.
+#android-ndk = <none> (path)
+
+# When targeting Android, specify the minimum API level to target.
+#android-api-level = 21
+
 # =============================================================================
 # General install configuration options
 # =============================================================================
@@ -700,6 +712,10 @@ changelog-seen = 2
 # the NDK for the target lives. This is used to find the C compiler to link and
 # build native code.
 # See `src/bootstrap/cc_detect.rs` for details.
+#
+# This option is deprecated as it requires building a standalone toolchain,
+# which is unnecessary with NDK r19 and newer. Instead, prefer to use the same
+# option under the [build] section.
 #android-ndk = <none> (path)
 
 # Build the sanitizer runtimes for this target.

src/bootstrap/cc_detect.rs

@@ -34,7 +34,7 @@ use crate::{Build, CLang, GitRepo};
 // so use some simplified logic here. First we respect the environment variable `AR`, then
 // try to infer the archiver path from the C compiler path.
 // In the future this logic should be replaced by calling into the `cc` crate.
-fn cc2ar(cc: &Path, target: TargetSelection) -> Option<PathBuf> {
+fn cc2ar(cc: &Path, target: TargetSelection, build: &Build) -> Option<PathBuf> {
     if let Some(ar) = env::var_os(format!("AR_{}", target.triple.replace("-", "_"))) {
         Some(PathBuf::from(ar))
     } else if let Some(ar) = env::var_os("AR") {
@@ -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") && build.config.android_ndk.is_some() {
+        Some(build.config.android_ndk.as_ref().unwrap().join("bin").join("llvm-ar"))
     } else {
         let parent = cc.parent().unwrap();
         let file = cc.file_name().unwrap().to_str().unwrap();
@@ -108,7 +110,7 @@ pub fn find(build: &mut Build) {
         let ar = if let ar @ Some(..) = config.and_then(|c| c.ar.clone()) {
             ar
         } else {
-            cc2ar(compiler.path(), target)
+            cc2ar(compiler.path(), target, build)
         };
 
         build.cc.insert(target, compiler.clone());
@@ -174,6 +176,16 @@ fn set_compiler(
                     .replace("thumbv7", "arm");
                 let compiler = format!("{}-{}", target, compiler.clang());
                 cfg.compiler(ndk.join("bin").join(compiler));
+            } else if let Some(ndk) = build.config.android_ndk.as_ref() {
+                let target = target
+                    .triple
+                    .replace("armv7neon", "armv7a")
+                    .replace("armv7", "armv7a")
+                    .replace("thumbv7neon", "armv7a")
+                    .replace("thumbv7", "armv7a");
+                let api_level = build.config.android_api_level.unwrap_or(21);
+                let compiler = format!("{}{}-{}", target, api_level, compiler.clang());
+                cfg.compiler(ndk.join("bin").join(compiler));
             }
         }
 

src/bootstrap/config.rs

@@ -75,6 +75,8 @@ pub struct Config {
     pub stage0_metadata: Stage0Metadata,
     /// Whether to use the `c` feature of the `compiler_builtins` crate.
     pub optimized_compiler_builtins: bool,
+    pub android_ndk: Option<PathBuf>,
+    pub android_api_level: Option<u32>,
 
     pub on_fail: Option<String>,
     pub stage: u32,
@@ -600,6 +602,8 @@ define_config! {
         patch_binaries_for_nix: Option<bool> = "patch-binaries-for-nix",
         metrics: Option<bool> = "metrics",
         optimized_compiler_builtins: Option<bool> = "optimized-compiler-builtins",
+        android_ndk: Option<PathBuf> = "android-ndk",
+        android_api_level: Option<u32> = "android-api-level",
     }
 }
 
@@ -951,6 +955,8 @@ impl Config {
         config.gdb = build.gdb.map(PathBuf::from);
         config.python = build.python.map(PathBuf::from);
         config.submodules = build.submodules;
+        config.android_ndk = build.android_ndk;
+        config.android_api_level = build.android_api_level;
         set(&mut config.low_priority, build.low_priority);
         set(&mut config.compiler_docs, build.compiler_docs);
         set(&mut config.docs_minification, build.docs_minification);