dev-manual: Added note about RPM not dealing with post-install

Fixes [YOCTO #10351]

I added a note to the "Post Installation Scripts" section of the
"Writing a New Recipe" section to call out the fact that the
RPM package manager will not install packages on the target when
any RPM post-install script returns a non-zero exit code when
the script is run on the target.

(From yocto-docs rev: 8565b0ba874f3357500a91640c0f77077c83b8d6)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/dev-manual-common-tasks.xml

@@ -3012,6 +3012,13 @@
                 If the script succeeds, the package is marked as installed.
                 If the script fails, the package is marked as unpacked and
                 the script is executed when the image boots again.
+                <note>
+                    Any RPM post-installation script that runs on the target
+                    should return a 0 exit code.
+                    RPM does not allow non-zero exit codes for these scripts,
+                    and the RPM package manager will cause the package to fail
+                    installation on the target.
+                </note>
             </para>
 
             <para>