Support NO_REBUILD=1 for testing without rebuild

Makefile

@@ -17,6 +17,11 @@
 # anywhere.  From the top level, the "all", "check", and "clean"
 # targets build, test, or clean everything.
 
+# To run test suites without rebuilding, pass NO_REBUILD=1 to the
+# build. This can be useful for testing binary interface compatibility
+# as it enables you to rebuild libraries and rerun tests without
+# relinking.
+
 # Although this is not a GNU package and does not use automake, you
 # can still run make clean to remove everything that is compiled, make
 # distclean to remove everything that is generated by the end user,
@@ -111,8 +116,12 @@ maintainer-clean: distclean
 	$(RM) autofiles.zip
 
 .PHONY: $(TEST_TARGETS)
+
+NO_REBUILD ?=
+ifneq ($(NO_REBUILD),1)
 $(foreach B,$(TEST_ITEMS),$(eval \
   check_$(B): $(TARGETS_$(B))))
+endif
 
 .PHONY: $(foreach B,$(BUILD_ITEMS),build_$(B))
 $(foreach B,$(BUILD_ITEMS),$(eval \

README.maintainer

@@ -1,6 +1,11 @@
 Release Reminders
 =================
 
+ * Test for binary compatility. The easiest way to do this is to check
+   out the last release, run the test suite, check out the new
+   release, run make build_libqpdf, check out the old release, and run
+   make check NO_REBUILD=1.
+
  * When making a release, always remember to run large file tests and
    image comparison tests (--enable-test-compare-images
    --with-large-file-test-path=/path).  For a major release, consider

TODO

@@ -55,9 +55,6 @@ General
    supported for the toolchains that support the install target
    (libtool).
 
- * Implement automated testing for binary compatibility and add to
-   release checklist.
-
  * Figure out how to find Visual Studio in Windows registry and see if
    I can get it to work with make so I can simplify creation of
    Windows releases.