android: Remove libstd hacks for unsupported Android APIs

Our minimum supported API version is 21, remove hacks to support older
Android APIs.

std/src/f32.rs

@@ -574,7 +574,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn log2(self) -> f32 {
-        crate::sys::log2f32(self)
+        unsafe { intrinsics::log2f32(self) }
     }
 
     /// Returns the base 10 logarithm of the number.

std/src/f64.rs

@@ -574,7 +574,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn log2(self) -> f64 {
-        crate::sys::log2f64(self)
+        unsafe { intrinsics::log2f64(self) }
     }
 
     /// Returns the base 10 logarithm of the number.

std/src/sys/pal/mod.rs

@@ -76,23 +76,5 @@ cfg_if::cfg_if! {
     }
 }
 
-#[cfg(not(test))]
-cfg_if::cfg_if! {
-    if #[cfg(target_os = "android")] {
-        pub use self::android::log2f32;
-        pub use self::android::log2f64;
-    } else {
-        #[inline]
-        pub fn log2f32(n: f32) -> f32 {
-            unsafe { crate::intrinsics::log2f32(n) }
-        }
-
-        #[inline]
-        pub fn log2f64(n: f64) -> f64 {
-            unsafe { crate::intrinsics::log2f64(n) }
-        }
-    }
-}
-
 #[cfg(not(target_os = "uefi"))]
 pub type RawOsError = i32;

std/src/sys/pal/unix/mod.rs

@@ -8,7 +8,6 @@ use crate::io::ErrorKind;
 pub mod weak;
 
 pub mod alloc;
-pub mod android;
 pub mod args;
 pub mod env;
 pub mod fd;
@@ -237,12 +236,8 @@ pub unsafe fn cleanup() {
 }
 
 #[allow(unused_imports)]
-#[cfg(not(target_os = "android"))]
 pub use libc::signal;
 
-#[cfg(target_os = "android")]
-pub use crate::sys::android::signal;
-
 #[inline]
 pub(crate) fn is_interrupted(errno: i32) -> bool {
     errno == libc::EINTR