Use llvm-strip with support for our cross-compilation targets

When stripping was introduced, it used the system `strip` binary from
GNU which isn't usually built to support cross-compilation.  On my
system I am greeted with the following error when `strip` runs:

    strip: Unable to recognise the format of the input file 'xxx/libevolve_android.so'

But obviously no-one checks process status codes -_-, so this command
"silently" continues without modifying the library.  That should have
left us with a functional yet fat/unstripped library.

When this feature was developed the same error message (and unstripped
library) was likely seen, resulting in a search for how to make the
format recognizable and ultimately having `--target=elf64-little` with
`// I'm told this should always be valid for Android, so use this as the
target` above it.  This is not a complete target and lacks the machine
and operating system, resulting in an invalid library that won't run on
Android.  It was removed in hopes of getting a valid binary, but there
is supposedly still an issue with loading the "unstripped?" library
(besides it not actually being stripped).

Just like all other compiler tools and linkers in `xbuild` use `strip`
from LLVM which has cross-compilation support (we already relied on
that when the `.so` was first compiled and linked...).  This infers the
right target from the file and automatically strips everything (i.e.
`--strip-all` is superfluous).

xbuild/src/command/build.rs

@@ -97,13 +97,12 @@ pub fn build(env: &BuildEnv) -> Result<()> {
                     std::fs::copy(&lib, unstripped_lib)
                         .expect("Could not copy lib before stripping its debug symbols");
 
-                    std::process::Command::new("strip")
-                        .arg("--strip-all")
-                        .arg(&lib)
-                        .spawn()
-                        .expect("Could not strip debug symbols from lib")
-                        .wait()
-                        .expect("Stripping of debug symbols from lib failed");
+                    let mut cmd = std::process::Command::new("llvm-strip");
+                    cmd.arg(&lib);
+                    let status = cmd
+                        .status()
+                        .with_context(|| format!("Could not run `{cmd:?}`"))?;
+                    ensure!(status.success(), "Failed to strip library using `{cmd:?}`");
                 }
 
                 let ndk = env.android_ndk();

xbuild/src/command/doctor.rs

@@ -18,8 +18,9 @@ impl Default for Doctor {
                     checks: vec![
                         Check::new("clang", Some(VersionCheck::new("--version", 0, 2))),
                         Check::new("clang++", Some(VersionCheck::new("--version", 0, 2))),
-                        Check::new("llvm-ar", None),
+                        Check::new("llvm-ar", Some(VersionCheck::new("--version", 1, 4))),
                         Check::new("llvm-lib", None),
+                        Check::new("llvm-strip", Some(VersionCheck::new("--version", 2, 4))),
                         Check::new("llvm-readobj", Some(VersionCheck::new("--version", 1, 4))),
                         Check::new("lld", Some(VersionCheck::new("-flavor ld --version", 0, 1))),
                         Check::new("lld-link", Some(VersionCheck::new("--version", 0, 1))),

xbuild/src/lib.rs

@@ -40,7 +40,7 @@ mod task;
 /// Current NDK version xbuild should use for Android.
 ///
 /// If this version is not available on a users machine xbuild will download it
-/// from our releases: ['https://github.com/Traverse-Research/xbuild/releases'].
+/// from our releases: https://github.com/Traverse-Research/xbuild/releases.
 ///
 /// The actual version used is determined by whatever the "ubuntu-latest" image has installed.
 const ANDROID_NDK_CURRENT: &str = "27.1.12297006";