scripts: add action to extract config from a build.log file

That got removed quite some time ago, but is really usefull to get the
configuration from a build.log file of a failing build.

1 files changed, 13 insertions, 4 deletions

diff --git a/docs/overview.txt b/docs/overview.txt
index 206e8c91..a0e12226 100644
--- a/docs/overview.txt
+++ b/docs/overview.txt
@@ -331,11 +331,20 @@ If you have an existing toolchain, you can re-use the options used to build it
 to create a new toolchain. That needs a very little bit of effort on your side
 but is quite easy. The options to build a toolchain are saved with the
 toolchain, and you can retrieve this configuration by running:
-  ${CT_TARGET}-config
+  ${CT_TARGET}-ct-ng.config
 
-This will dump the configuration to stdout, so to rebuild a toolchain with this
-configuration, the following is all you need to do:
-  ${CT_TARGET}-config >.config
+An alternate method is to extract the configuration from a build.log file.
+This will be necessary if your toolchain was build with crosstool-NG prior
+to 1.4.0, but can be used with build.log files from any version:
+  ct-ng extractconfig <build.log >.config
+
+Or, if your build.log file is compressed (most probably!):
+  bzcat build.log.bz2 |ct-ng extractconfig >.config
+
+The above commands will dump the configuration to stdout, so to rebuild a
+toolchain with this configuration, just redirect the output to the
+.config file:
+  ${CT_TARGET}-ct-ng.config >.config
   ct-ng oldconfig
 
 Then, you can review and change the configuration by running: