ENH: Compile git with SSL support

Older versions of git included in older linux distributions are not able
to download source from Github. A newer version is required with a newer
OpenSSL. This requires to also build curl with the same OpenSSL.

CMake is downloaded precompiled if available (64bits system) or compiled
from source otherwise.

imagefiles/utils.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+set -e
+
+# Copied from https://github.com/pypa/manylinux/blob/master/docker/build_scripts/build_utils.sh
+function check_var {
+    if [ -z "$1" ]; then
+        echo "required variable not defined"
+        exit 1
+    fi
+}
+
+# Copied from https://github.com/pypa/manylinux/blob/master/docker/build_scripts/build_utils.sh
+function check_sha256sum {
+    local fname=$1
+    check_var ${fname}
+    local sha256=$2
+    check_var ${sha256}
+
+    echo "${sha256}  ${fname}" > ${fname}.sha256
+    sha256sum -c ${fname}.sha256
+    rm -f ${fname}.sha256
+}
+