[Buildroot] [git commit] docs/manual: fix typo in name of a qmake-package variable

[Peter Korsgaard]

>>>>> "Yann" == Yann E MORIN <yann.morin.1998 at free.fr> writes:

 > commit: https://git.buildroot.net/buildroot/commit/?id=ac2db5eb2e6091a05d1cd3d641213ab01ddb0aa2
 > branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/master

 > Since commit 39d334faa5c1 (package/pkg-qmake: add <pkg>_SYNC_QT_HEADERS
 > support), the qmake-package infra recognises said variable but the
 > manual has the wrong variable name, which is missing the "_QT" part.

 > We fix that by amending the manual to document the proper variable name.

 > Signed-off-by: Yann E. MORIN <yann.morin.1998 at free.fr>

Committed to 2021.02.x and 2021.05.x, thanks.

-- 
Bye, Peter Korsgaard