ci: test fedora 21

Author: Wenzel

.github/builder/Dockerfile

@@ -1,5 +1,5 @@
 # hadolint global ignore=DL3033,SC3044
-FROM fedora:20@sha256:5d5a02b873d298da9bca4b84440c5cd698b0832560c850d92cf389cef58bc549
+FROM fedora:21
 
 ENV PATH="${PATH}:/root/.cargo/bin/"
 

.github/builder/common.sh

@@ -87,7 +87,7 @@ download_and_verify_make() {
         curl -L -o "${BUILDER_DIR}/rsrc/gnu-keyring.gpg" \
             "${GNU_GPG_KEYRING_URL}"
         gpg --no-default-keyring --keyring "${BUILDER_DIR}/rsrc/gnu-keyring.gpg" --import \
-            "${BUILDER_DIR}/rsrc/gnu-keyring.gpg"
+            "${BUILDER_DIR}/rsrc/gnu-keyring.gpg" || true
     fi
 
     if [ ! -f "${BUILDER_DIR}/rsrc/make-4.4.1.tar.gz" ]; then
@@ -222,7 +222,7 @@ download_and_verify_builder_rpms() {
         # NOTE: This may stop working at some point, as Fedora 20 is EOL. Therefore, we download the
         # packages with the expectation that we will provide them separately if they are no longer
         # available.
-        docker run -v "${BUILDER_DIR}/rsrc/rpms:/rpms" fedora:20 bash -c \
+        docker run -v "${BUILDER_DIR}/rsrc/rpms:/rpms" fedora:21 bash -c \
             'yum -y update && yum install --downloadonly --downloaddir=/rpms coreutils gcc gcc-c++ make which && chmod -R 755 /rpms/'
     fi
 }