Build environment
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+CONTINUOUS INTEGRATION SCRIPTS
+==============================
+
+Environment Variables Used in Build Scripts
+-------------------------------------------
+
+- `NODE_LABELS`: the variable defines a list of OS properties. The set values are used by the
+ build scripts to select proper behavior for different OS.
+
+ The list should include at least `[OS_TYPE]`, `[DISTRO_TYPE]`, and `[DISTRO_VERSION]`.
+
+ Possible values for Linux:
+
+ * `[OS_TYPE]`: `Linux`
+ * `[DISTRO_TYPE]`: `Ubuntu`
+ * `[DISTRO_VERSION]`: `Ubuntu-16.04`, `Ubuntu-18.04`
+
+ Possible values for OS X / macOS:
+
+ * `[OS_TYPE]`: `OSX`
+ * `[DISTRO_TYPE]`: `OSX` (can be absent)
+ * `[DISTRO_VERSION]`: `OSX-10.11`, `OSX-10.12`, `OSX-10.13`
+
+- `JOB_NAME`: optional variable to define type of the job. Depending on the defined job type,
+ the build scripts can perform different tasks.
+
+ Possible values:
+
+ * empty: default build process
+ * `code-coverage` (Linux OS is assumed): debug build with tests and code coverage analysis
+ * `limited-build`: only a single debug build with tests
+
+- `CACHE_DIR`: the variable defines a path to folder containing cached files from previous builds,
+ e.g., a compiled version of ndn-cxx library. If not set, `/tmp` is used.
+
+- `WAF_JOBS`: number of parallel build jobs used by waf, defaults to 1.