readelf: Prune gaps warning in build notes

Since some object files may not have build notes, it is normal to have
gaps in build notes.

	PR binutils/23898
	* testsuite/lib/binutils-common.exp (prune_warnings_extra):
	Prune gaps in build notes.

binutils/testsuite/lib/binutils-common.exp

@@ -442,6 +442,8 @@ proc prune_warnings_extra { text } {
 	# The "\\1" is to try to preserve a "\n" but only if necessary.
 	regsub -all "(^|\n)(\[^\n\]*: warning:\[^\n\]*unsupported GNU_PROPERTY_TYPE\[^\n\]*\n?)+" $text "\\1" text
     }
+    # PR binutils/23898: It is OK to have gaps in build notes.
+    regsub -all "(^|\n)(\[^\n\]*: Warning: Gap in build notes detected from\[^\n\]*\n?)+" $text "\\1" text
     return $text
 }