Include Linux atomic emulation on androideabi

The old androideabi uses armv5 and thus also needs the atomic emulation
and because Android is basically Linux it can use the same
implementation.

build.rs

@@ -69,8 +69,11 @@ fn main() {
         println!("cargo:rustc-cfg=thumb_1")
     }
 
-    // Only emit the ARM Linux atomic emulation on pre-ARMv6 architectures.
-    if llvm_target[0] == "armv4t" || llvm_target[0] == "armv5te" {
+    // Only emit the ARM Linux atomic emulation on pre-ARMv6 architectures. This
+    // includes the old androideabi. It is deprecated but it is available as a
+    // rustc target (arm-linux-androideabi).
+    if llvm_target[0] == "armv4t" || llvm_target[0] == "armv5te" || llvm_target[2] == "androideabi"
+    {
         println!("cargo:rustc-cfg=kernel_user_helpers")
     }
 }

src/lib.rs

@@ -49,7 +49,11 @@ pub mod mem;
 #[cfg(target_arch = "arm")]
 pub mod arm;
 
-#[cfg(all(kernel_user_helpers, target_os = "linux", target_arch = "arm"))]
+#[cfg(all(
+    kernel_user_helpers,
+    any(target_os = "linux", target_os = "android"),
+    target_arch = "arm"
+))]
 pub mod arm_linux;
 
 #[cfg(any(target_arch = "riscv32"))]