sdk-manual: correctly describe separate build-sysroots tasks in direct sdk workflows

They were separated in
https://git.yoctoproject.org/poky/commit/?id=63e53fb8b60d38315015844bd3357fa1649cd639

(From yocto-docs rev: 7cb8ee0b922c57a2fc7100eca585463e888964be)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

documentation/sdk-manual/extensible.rst

@@ -74,7 +74,7 @@ Setting up the Extensible SDK environment directly in a Yocto build
       $ bitbake meta-ide-support
       $ bitbake -c populate_sysroot gtk+3
       # or any other target or native item that the application developer would need
-      $ bitbake build-sysroots
+      $ bitbake build-sysroots -c build_native_sysroot && bitbake build-sysroots -c build_target_sysroot
 
 Setting up the Extensible SDK from a standalone installer
 ---------------------------------------------------------
@@ -1226,8 +1226,12 @@ In this scenario, the Yocto build tooling, e.g. ``bitbake``
 is directly accessible to build additional items, and it
 can simply be executed directly::
 
+   $ bitbake curl-native
+   # Add newly built native items to native sysroot
+   $ bitbake build-sysroots -c build_native_sysroot
    $ bitbake mesa
-   $ bitbake build-sysroots
+   # Add newly built target items to target sysroot
+   $ bitbake build-sysroots -c build_target_sysroot
 
 When using a standalone installer for the Extensible SDK
 --------------------------------------------------------