build+ci: switch to python3

Also in this commit:
 * Sync CI scripts with other projects
 * Modernize docs/conf.py
 * Cleanup README.md
 * Use the official markdown version of the GPLv3

Refs: #5095
Change-Id: Ie607fcde1f6e41fa5efbbb41b21cb08583017442
diff --git a/.jenkins.d/01-ndn-cxx.sh b/.jenkins.d/01-ndn-cxx.sh
index e627627..7bf1cfe 100755
--- a/.jenkins.d/01-ndn-cxx.sh
+++ b/.jenkins.d/01-ndn-cxx.sh
@@ -1,12 +1,7 @@
 #!/usr/bin/env bash
-set -e
+set -ex
 
-JDIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
-source "$JDIR"/util.sh
-
-set -x
-
-pushd "${CACHE_DIR:-/tmp}" >/dev/null
+pushd "$CACHE_DIR" >/dev/null
 
 INSTALLED_VERSION=
 if has OSX $NODE_LABELS; then
@@ -22,17 +17,15 @@
     INSTALLED_VERSION=$(git -C ndn-cxx rev-parse HEAD 2>/dev/null || echo NONE)
 fi
 
-sudo rm -Rf ndn-cxx-latest
-
-git clone --depth 1 git://github.com/named-data/ndn-cxx ndn-cxx-latest
-
+sudo rm -rf ndn-cxx-latest
+git clone --depth 1 https://github.com/named-data/ndn-cxx.git ndn-cxx-latest
 LATEST_VERSION=$(git -C ndn-cxx-latest rev-parse HEAD 2>/dev/null || echo UNKNOWN)
 
 if [[ $INSTALLED_VERSION != $LATEST_VERSION ]]; then
-    sudo rm -Rf ndn-cxx
+    sudo rm -rf ndn-cxx
     mv ndn-cxx-latest ndn-cxx
 else
-    sudo rm -Rf ndn-cxx-latest
+    sudo rm -rf ndn-cxx-latest
 fi
 
 sudo rm -f /usr/local/bin/ndnsec*
@@ -42,15 +35,25 @@
 
 pushd ndn-cxx >/dev/null
 
-./waf configure --color=yes --enable-shared --disable-static --without-osx-keychain
-./waf build --color=yes -j${WAF_JOBS:-1}
-sudo_preserve_env PATH -- ./waf install --color=yes
+if has Linux $NODE_LABELS && [[ $CXX != clang* && -z $DISABLE_ASAN ]]; then
+    # https://stackoverflow.com/a/47022141
+    ASAN="--with-sanitizer=address"
+fi
+if has CentOS-8 $NODE_LABELS; then
+    # https://bugzilla.redhat.com/show_bug.cgi?id=1721553
+    PCH="--without-pch"
+fi
+
+./waf --color=yes configure --disable-static --enable-shared --without-osx-keychain $ASAN $PCH
+./waf --color=yes build -j$WAF_JOBS
+sudo_preserve_env PATH -- ./waf --color=yes install
 
 popd >/dev/null
 popd >/dev/null
 
+if has CentOS-8 $NODE_LABELS; then
+    sudo tee /etc/ld.so.conf.d/ndn.conf >/dev/null <<< /usr/local/lib64
+fi
 if has Linux $NODE_LABELS; then
     sudo ldconfig
-elif has FreeBSD10 $NODE_LABELS; then
-    sudo ldconfig -m
 fi