[PATCH] doc: Update sudo configuration in the manual.

[Henning Schild <henning.schild@siemens.com>]

Francesco reported build problems with the suggested sudo configuration.
The issue might be that somewhere along the way a user or group other
than root is used, or that there are problems with (NO)SETENV.

Update the manual to include an entry that should prevent such problems,
also add a line to deal with proxies.

Reported-by: Francesco <fdprnd@dave.eu>
Signed-off-by: Henning Schild <henning.schild@siemens.com>
---
 doc/user_manual.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/doc/user_manual.md b/doc/user_manual.md
index 7bdfc1c..70c382e 100644
--- a/doc/user_manual.md
+++ b/doc/user_manual.md
@@ -79,9 +79,11 @@ Isar requires `sudo` rights without password to work with `chroot` and `debootst
 ```
 In the editor, allow the current user to run sudo without a password, e.g.:
 ```
- <user>  ALL=NOPASSWD: ALL
+ <user>  ALL=(ALL:ALL) NOPASSWD:ALL
+ Defaults env_keep += "ftp_proxy http_proxy https_proxy no_proxy"
 ```
 Replace `<user>` with your user name. Use the tab character between the user name and parameters.
+The second line will make sure your proxy settings will not get lost when using `sudo`. Include it if you are in the unfortunate possition to having to deal with that.
 
 ### Check out Isar
 
-- 
2.16.1