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/build-and-install-curl.sh

@@ -0,0 +1,49 @@
+#!/bin/bash
+
+set -ex
+
+MY_DIR=$(dirname "${BASH_SOURCE[0]}")
+source $MY_DIR/utils.sh
+
+#
+# Function 'do_curl_build' and 'build_curl'
+# copied from https://github.com/pypa/manylinux/tree/master/docker/build_scripts
+#
+
+CURL_ROOT=curl_7.52.1
+CURL_HASH=a8984e8b20880b621f61a62d95ff3c0763a3152093a9f9ce4287cfd614add6ae
+
+# We had to switch to a debian mirror because we can't use TLS until we
+# bootstrap it with this curl + openssl
+CURL_DOWNLOAD_URL=http://deb.debian.org/debian/pool/main/c/curl
+
+function do_curl_build {
+    # We do this shared to avoid obnoxious linker issues where git couldn't
+    # link properly. If anyone wants to make this build statically go for it.
+    LIBS=-ldl CFLAGS=-Wl,--exclude-libs,ALL ./configure --with-ssl --disable-static > /dev/null
+    make > /dev/null
+    make install > /dev/null
+}
+
+
+function build_curl {
+    local curl_fname=$1
+    check_var ${curl_fname}
+    local curl_sha256=$2
+    check_var ${curl_sha256}
+    check_var ${CURL_DOWNLOAD_URL}
+    # Can't use curl here because we don't have it yet...we are building it.
+    wget -q ${CURL_DOWNLOAD_URL}/${curl_fname}.orig.tar.gz
+    check_sha256sum ${curl_fname}.orig.tar.gz ${curl_sha256}
+    tar -zxf ${curl_fname}.orig.tar.gz
+    (cd curl-* && do_curl_build)
+    rm -rf curl_*
+}
+
+cd /usr/src
+build_curl $CURL_ROOT $CURL_HASH
+
+(cat /etc/ld.so.conf.d/usr-local.conf 2> /dev/null | grep -q "^/usr/local/lib$") ||
+  echo '/usr/local/lib' >> /etc/ld.so.conf.d/usr-local.conf
+ldconfig
+