Library ABI tracking with abigail

Provide two make targets: checkabi and storeabi.

storeabi uses libabigail to generate a reference copy of the ABI for the
public libraries.

checkabi compares such a reference to the compiled version, failing if
they are not compatible.  No ABI is generated for libzpool.so, it is
only used by ztest and zdb and not external consumers.

Co-authored-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Antonio Russo <aerusso@aerusso.net>
Closes #11144

Makefile.am

@@ -136,6 +136,13 @@ shellcheck:
 		echo "skipping shellcheck because shellcheck is not installed"; \
 	fi
 
+PHONY += checkabi storeabi
+checkabi: lib
+	$(MAKE) -C lib checkabi
+
+storeabi: lib
+	$(MAKE) -C lib storeabi
+
 PHONY += checkbashisms
 checkbashisms:
 	@if type checkbashisms > /dev/null 2>&1; then \