man: Add list of flags set by bug feature area

debian/changelog

@@ -94,6 +94,7 @@ dpkg (1.18.5) UNRELEASED; urgency=medium
       Closes: #795163
     - Update field requirements of control file formats to match dpkg reality.
     - Document the format of the origins filename in deb-origin(5).
+    - Add list of flags set by bug feature area to dpkg-buildflags(1).
 
   [ Updated programs translations ]
   * Portuguese (Miguel Figueiredo).

man/dpkg-buildflags.1

@@ -222,6 +222,11 @@ problems in the source code or build system.
 .B bug
 This setting (disabled by default) adds any warning option that reliably
 detects problematic source code. The warnings are fatal.
+The only currently supported flags are \fBCFLAGS\fP and \fBCXXFLAGS\fP
+with flags set to \fB\-Werror=array\-bounds\fP, \fB\%\-Werror=clobbered\fP,
+\fB\%\-Werror=implicit\-function\-declaration\fP and
+\fB\%\-Werror=volatile\-register\-var\fP.
+.
 .TP
 .B canary
 This setting (disabled by default) adds dummy canary options to the build