Remove build.rs for Android when assuming API level is always >=21

Since Rust 1.82 the minimum Android API level is 21.  In
`backtrace`, this warranted the removal of the API version check via
`__ANDROID_API__` in rust-lang/backtrace-rs#656
since it is now always known to be >=21.  When `findshlibs` bumps its
MSRV the same could be done.

This change is sparked by a long search for why backtraces always had
`<unknown>` symbols on Android - and when solving that by upgrading Rust
(for `std::backtrace`) or our `backtrace` dependency, why Sentry reports
did not record what images/libraries were loaded at which offsets to
resolve stack addresses back to function symbols.  It turned out that
the `xbuild` build tool never set `__ANDROID_API__` (by not telling
`clang` about the target API level via the triple) which would cause
this code to never set `feature = "dl_iterate_phdr"` to search for
libraries on Android: rust-mobile/xbuild#209

Cargo.toml

@@ -8,15 +8,11 @@ keywords = ["dyld", "dylib", "shared", "library", "dl_iterate_phdr"]
 license = "MIT OR Apache-2.0"
 readme = "./README.md"
 repository = "https://github.com/gimli-rs/findshlibs"
+rust-version = "1.82"
 
 [dependencies]
 libc = "0.2.104"
 
-[build-dependencies]
-# Only needed for Android, but cannot be target dependent
-# https://github.com/rust-lang/cargo/issues/4932
-cc = "1.0.67"
-
 [target.'cfg(any(target_os = "macos", target_os = "ios"))'.dependencies]
 lazy_static = "1.4"
 

src/lib.rs

@@ -100,25 +100,18 @@
 #[cfg(any(target_os = "macos", target_os = "ios"))]
 pub mod macos;
 
-#[cfg(any(
-    target_os = "linux",
-    all(target_os = "android", feature = "dl_iterate_phdr")
-))]
+#[cfg(any(target_os = "linux", target_os = "android"))]
 pub mod linux;
 
 #[cfg(target_os = "windows")]
 pub mod windows;
 
 use std::ffi::OsStr;
 use std::fmt::{self, Debug};
-use std::usize;
 
 pub mod unsupported;
 
-#[cfg(any(
-    target_os = "linux",
-    all(target_os = "android", feature = "dl_iterate_phdr")
-))]
+#[cfg(any(target_os = "linux", target_os = "android"))]
 use crate::linux as native_mod;
 
 #[cfg(any(target_os = "macos", target_os = "ios"))]
@@ -131,7 +124,7 @@ use crate::windows as native_mod;
     target_os = "macos",
     target_os = "ios",
     target_os = "linux",
-    all(target_os = "android", feature = "dl_iterate_phdr"),
+    target_os = "android",
     target_os = "windows"
 )))]
 use unsupported as native_mod;
@@ -145,7 +138,7 @@ pub const TARGET_SUPPORTED: bool = cfg!(any(
     target_os = "macos",
     target_os = "ios",
     target_os = "linux",
-    all(target_os = "android", feature = "dl_iterate_phdr"),
+    target_os = "android",
     target_os = "windows"
 ));