Move to devtoolset-9

Allows the use of C++17 features like std::filesystem in projects like
libappimage, AppImageUpdate.

Author: TheAssassin

Dockerfile.centos7-i386

@@ -8,8 +8,8 @@ ARG VERBOSE=0
 # thanks CloudLinux, you're really helping us poor AppImage creators seeking for maximum compatibility by providing devtoolset i386 builds
 RUN yum install -y yum-utils && \
     rpm --import https://repo.cloudlinux.com/cloudlinux/security/RPM-GPG-KEY-CloudLinux && \
-    yum-config-manager --add-repo https://www.repo.cloudlinux.com/cloudlinux/7/sclo/devtoolset-8/i386/ && \
-    yum install -y devtoolset-8 \
+    yum-config-manager --add-repo https://www.repo.cloudlinux.com/cloudlinux/7/sclo/devtoolset-9/i386/ && \
+    yum install -y devtoolset-9 \
         wget make gnupg zip git subversion glib2-devel automake libtool patch zlib-devel cairo-devel openssl-devel curl-devel \
         fuse-devel vim-common zlib-devel desktop-file-utils fuse fuse-libs gtest-devel \
         libXft-devel librsvg2-devel curl libffi-devel gettext-devel file python2 bzip2 \

Dockerfile.centos7-x86_64

@@ -6,7 +6,7 @@ ENV ARCH=x86_64 DIST=centos7
 ARG VERBOSE=0
 
 RUN yum install -y centos-release-scl && \
-    yum install -y devtoolset-8 \
+    yum install -y devtoolset-9 \
         wget make gnupg zip git subversion glib2-devel automake libtool patch zlib-devel cairo-devel openssl-devel curl-devel \
         fuse-devel vim-common zlib-devel desktop-file-utils fuse fuse-libs gtest-devel \
         libXft-devel librsvg2-devel curl libffi-devel gettext-devel file python2 bzip2 \

entrypoint-centos.sh

@@ -2,7 +2,7 @@
 
 set -eo pipefail
 
-source /opt/rh/devtoolset-8/enable
+source /opt/rh/devtoolset-9/enable
 
 export PATH=/deps/bin/:"$PATH"
 export PKG_CONFIG_PATH=/deps/lib/pkgconfig:"$PKG_CONFIG_PATH"