Use own prebuilt CMake

Author: TheAssassin

travis/Dockerfile

@@ -4,7 +4,7 @@ SHELL ["/bin/bash", "-x", "-c"]
 
 RUN yum install -y centos-release-scl-rh && \
     yum install -y devtoolset-7 wget curl patchelf vim-common fuse libfuse2 libtool autoconf automake zlib-devel libjpeg-devel libpng-devel nano git && \
-    wget https://github.com/Kitware/CMake/releases/download/v3.13.4/cmake-3.13.4-Linux-x86_64.tar.gz -O- | tar xz --strip-components=1 -C/usr/local
+    wget https://artifacts.assassinate-you.net/artifactory/cmake-centos6/cmake-v3.15.3-x86_64.tar.gz -O- | tar xz --strip-components=1 -C/usr/local
 
 ENV ARCH=x86_64
 COPY entrypoint.sh /

travis/Dockerfile.i386

@@ -19,12 +19,4 @@ ENV ARCH=i386
 ENTRYPOINT ["/entrypoint.sh"]
 SHELL ["/entrypoint.sh", "bash", "-x", "-c"]
 
-# old git doesn't support cloning tags with -b, therefore cloning remote HEAD and then manually checking out the requested tag
-RUN git clone https://github.com/Kitware/CMake && \
-    cd CMake && \
-    git checkout v3.14.3 && \
-    ./configure --prefix=/usr/local --parallel=$(nproc) && \
-    make -j$(nproc) all && \
-    make install && \
-    cd .. && \
-    rm -r CMake/
+RUN wget https://artifacts.assassinate-you.net/artifactory/cmake-centos6/cmake-v3.15.3-i386.tar.gz -O- | tar xz --strip-components=1 -C/usr/local