ci+docs: minor cleanups

Change-Id: I280fd84d89061e34ad4e2aaa00ce63ad21b03565
diff --git a/.jenkins.d/10-build.sh b/.jenkins.d/10-build.sh
index dd63348..f2ddf0c 100755
--- a/.jenkins.d/10-build.sh
+++ b/.jenkins.d/10-build.sh
@@ -4,17 +4,17 @@
 git submodule sync
 git submodule update --init
 
+if [[ -z $DISABLE_ASAN ]]; then
+    ASAN="--with-sanitizer=address"
+fi
+if [[ $JOB_NAME == *"code-coverage" ]]; then
+    COVERAGE="--with-coverage"
+fi
 if has CentOS-8 $NODE_LABELS; then
     # https://bugzilla.redhat.com/show_bug.cgi?id=1721553
     PCH="--without-pch"
 fi
 
-if [[ $JOB_NAME == *"code-coverage" ]]; then
-    COVERAGE="--with-coverage"
-elif [[ -z $DISABLE_ASAN ]]; then
-    ASAN="--with-sanitizer=address"
-fi
-
 if [[ $JOB_NAME != *"code-coverage" && $JOB_NAME != *"limited-build" ]]; then
     # Build static library in release mode with tests and without precompiled headers
     ./waf --color=yes configure --enable-static --disable-shared --with-tests --without-pch
diff --git a/.jenkins.d/README.md b/.jenkins.d/README.md
index 9087f0f..e8dbf37 100644
--- a/.jenkins.d/README.md
+++ b/.jenkins.d/README.md
@@ -22,4 +22,7 @@
   - `code-coverage`: debug build with tests and code coverage analysis (Ubuntu Linux is assumed)
   - `limited-build`: only a single debug build with tests
 
+- `CACHE_DIR`: directory containing cached files from previous builds, e.g., a compiled version
+  of ndn-cxx. If not set, `/tmp` is used.
+
 - `WAF_JOBS`: number of parallel build threads used by waf, defaults to 1.