Document '--only-configure' flag

Cabal/doc/nix-local-build.rst

@@ -368,6 +368,12 @@ cause extra store packages to be built (for example,
 ``--enable-profiling`` will automatically make sure profiling libraries
 for all transitive dependencies are built and installed.)
 
+In addition ``cabal new-build`` accepts these flags:
+
+- ``--only-configure``: When given we will forgoe performing a full build and
+  abort after running the configure phase of each target package.
+
+
 cabal new-repl
 --------------
 

cabal-install/changelog

@@ -3,6 +3,7 @@
 2.6.0.0 (current development version)
 	* New solver flag: '--reject-unconstrained-dependencies'. (#2568)
 	* "cabal new-repl" now works for indefinite (in the Backpack sense) components.
+	* New v2-build flag: '--only-configure'. (#5578)
 
 2.4.0.1
 	* 'new-sdist' now generates tarballs with file modification