docs: add notes about tools/config-gen

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/Documentation/howto-build-sys.txt b/Documentation/howto-build-sys.txt
index 53566140ebb3cc1df47bcd1b738e118f0823da20..36f8e3035ef6f699decabae9ae5420bb03cf2565 100644 (file)
--- a/Documentation/howto-build-sys.txt
+++ b/Documentation/howto-build-sys.txt
@@ -31,3 +31,26 @@ util-linux build system
                   ...) is missing an error is printed and ./configure aborted
 
        "no"    - the util/feature is unwanted
+
+
+ - some basic scenarios for the ./configure script are defined in the
+   tools/config-gen.d/ directory. If you want to use these predefined scenarios
+   then call
+
+       ./tools/config-gen [<scenario> ...]
+
+   for example
+
+       ./tools/config-gen all selinux
+
+   will build all utils with enabled selinux support. You can also define some
+   CFLAGS, for example:
+
+       CFLAGS=$(rpm --eval '%optflags') ./tools/config-gen all
+
+   will use the default distro flags.
+
+ - the tools/config-gen script is also used for build system regression tests,
+   the test is not enabled by default, you have to use
+
+       tests/run.sh build-sys --force