add rpmdevtools and import epel gpg key

Dockerfile

@@ -6,6 +6,8 @@ LABEL maintainer="Robert Kaussow <mail@geeklabor.de>" \
     org.label-schema.vendor="Robert Kaussow" \
     org.label-schema.schema-version="1.0"
 
+ADD overlay/ /
+
 RUN yum install -q -y \
     gcc gcc-c++ \
     libtool libtool-ltdl \
@@ -31,10 +33,10 @@ RUN yum install -q -y \
     pkgconfig \
     wget curl \
     automake autoconf \
-    yum-utils rpm-build \
+    yum-utils rpm-build rpmdevtools \
     epel-release && \
-    yum clean all && \
-    echo '%_topdir /drone/src' > /root/.rpmmacros
+    rpm --import https://dl.fedoraproject.org/pub/epel/RPM-GPG-KEY-EPEL-7 && \
+    yum clean all
 
 USER root