diff --git a/ci/build.sh b/ci/build.sh
index 512c9cfc9a12a..722626b43d686 100644
--- a/ci/build.sh
+++ b/ci/build.sh
@@ -11,6 +11,7 @@ set -ex
 : "${OS?The OS environment variable must be set.}"
 
 RUST=${TOOLCHAIN}
+VERBOSE=-v
 
 echo "Testing Rust ${RUST} on ${OS}"
 
@@ -41,50 +42,50 @@ test_target() {
 
     # Test that libc builds without any default features (no std)
     if [ "${NO_STD}" != "1" ]; then
-        cargo "+${RUST}" "${BUILD_CMD}" -vv --no-default-features --target "${TARGET}"
+        cargo "+${RUST}" "${BUILD_CMD}" "$VERBOSE" --no-default-features --target "${TARGET}"
     else
         # FIXME: With `build-std` feature, `compiler_builtins` emits a lof of lint warnings.
         RUSTFLAGS="-A improper_ctypes_definitions" cargo "+${RUST}" "${BUILD_CMD}" \
-            -Z build-std=core,alloc -vv --no-default-features --target "${TARGET}"
+            -Z build-std=core,alloc "$VERBOSE" --no-default-features --target "${TARGET}"
     fi
     # Test that libc builds with default features (e.g. std)
     # if the target supports std
     if [ "$NO_STD" != "1" ]; then
-        cargo "+${RUST}" "${BUILD_CMD}" -vv --target "${TARGET}"
+        cargo "+${RUST}" "${BUILD_CMD}" "$VERBOSE" --target "${TARGET}"
     else
         RUSTFLAGS="-A improper_ctypes_definitions" cargo "+${RUST}" "${BUILD_CMD}" \
-            -Z build-std=core,alloc -vv --target "${TARGET}"
+            -Z build-std=core,alloc "$VERBOSE" --target "${TARGET}"
     fi
 
     # Test that libc builds with the `extra_traits` feature
     if [ "${NO_STD}" != "1" ]; then
-        cargo "+${RUST}" "${BUILD_CMD}" -vv --no-default-features --target "${TARGET}" \
+        cargo "+${RUST}" "${BUILD_CMD}" "$VERBOSE" --no-default-features --target "${TARGET}" \
             --features extra_traits
     else
         RUSTFLAGS="-A improper_ctypes_definitions" cargo "+${RUST}" "${BUILD_CMD}" \
-            -Z build-std=core,alloc -vv --no-default-features \
+            -Z build-std=core,alloc "$VERBOSE" --no-default-features \
             --target "${TARGET}" --features extra_traits
     fi
 
     # Test the 'const-extern-fn' feature on nightly
     if [ "${RUST}" = "nightly" ]; then
         if [ "${NO_STD}" != "1" ]; then
-            cargo "+${RUST}" "${BUILD_CMD}" -vv --no-default-features --target "${TARGET}" \
+            cargo "+${RUST}" "${BUILD_CMD}" "$VERBOSE" --no-default-features --target "${TARGET}" \
                 --features const-extern-fn
         else
             RUSTFLAGS="-A improper_ctypes_definitions" cargo "+${RUST}" "${BUILD_CMD}" \
-                -Z build-std=core,alloc -vv --no-default-features \
+                -Z build-std=core,alloc "$VERBOSE" --no-default-features \
                 --target "${TARGET}" --features const-extern-fn
         fi
     fi
 
     # Also test that it builds with `extra_traits` and default features:
     if [ "$NO_STD" != "1" ]; then
-        cargo "+${RUST}" "${BUILD_CMD}" -vv --target "${TARGET}" \
+        cargo "+${RUST}" "${BUILD_CMD}" "$VERBOSE" --target "${TARGET}" \
             --features extra_traits
     else
         RUSTFLAGS="-A improper_ctypes_definitions" cargo "+${RUST}" "${BUILD_CMD}" \
-            -Z build-std=core,alloc -vv --target "${TARGET}" \
+            -Z build-std=core,alloc "$VERBOSE" --target "${TARGET}" \
             --features extra_traits
     fi
 }
diff --git a/libc-test/Cargo.toml b/libc-test/Cargo.toml
index 8d85ad794ed53..df1bd04abd7d9 100644
--- a/libc-test/Cargo.toml
+++ b/libc-test/Cargo.toml
@@ -1,6 +1,7 @@
 [package]
 name = "libc-test"
 version = "0.2.151"
+edition = "2018"
 authors = ["The Rust Project Developers"]
 license = "MIT OR Apache-2.0"
 build = "build.rs"
diff --git a/libc-test/build.rs b/libc-test/build.rs
index ec55fadea1ba9..9560e07c8cf7e 100644
--- a/libc-test/build.rs
+++ b/libc-test/build.rs
@@ -82,8 +82,7 @@ fn do_semver() {
     let target_env = env::var("CARGO_CFG_TARGET_ENV").unwrap();
 
     // `libc-test/semver` dir.
-    let mut semver_root = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
-    semver_root.push("semver");
+    let mut semver_root = PathBuf::from("semver");
 
     // NOTE: Windows has the same `family` as `os`, no point in including it
     // twice.
@@ -93,7 +92,10 @@ fn do_semver() {
     if family != os && os != "android" {
         process_semver_file(&mut output, &mut semver_root, &family);
     }
-    process_semver_file(&mut output, &mut semver_root, &vendor);
+    // We don't do semver for unknown targets.
+    if vendor != "unknown" {
+        process_semver_file(&mut output, &mut semver_root, &vendor);
+    }
     process_semver_file(&mut output, &mut semver_root, &os);
     let os_arch = format!("{}-{}", os, arch);
     process_semver_file(&mut output, &mut semver_root, &os_arch);
@@ -141,6 +143,9 @@ fn process_semver_file<W: Write, P: AsRef<Path>>(output: &mut W, path: &mut Path
 }
 
 fn main() {
+    // Avoid unnecessary re-building.
+    println!("cargo:rerun-if-changed=build.rs");
+
     do_cc();
     do_ctest();
     do_semver();
diff --git a/src/unix/linux_like/linux/uclibc/mod.rs b/src/unix/linux_like/linux/uclibc/mod.rs
index 79897ac78fae0..32c65545a8905 100644
--- a/src/unix/linux_like/linux/uclibc/mod.rs
+++ b/src/unix/linux_like/linux/uclibc/mod.rs
@@ -431,6 +431,7 @@ extern "C" {
     pub fn setrlimit(resource: ::__rlimit_resource_t, rlim: *const ::rlimit) -> ::c_int;
     pub fn getpriority(which: ::__priority_which_t, who: ::id_t) -> ::c_int;
     pub fn setpriority(which: ::__priority_which_t, who: ::id_t, prio: ::c_int) -> ::c_int;
+    pub fn getauxval(type_: ::c_ulong) -> ::c_ulong;
 }
 
 cfg_if! {