runtime(make): Prevent makeTargetinDefine matching extra line

runtime(make): Prevent makeTargetinDefine matching extra line

This fixes a bug introduced in 2a33b499a3d7f46dc307234847a6562cef6cf1d8:
When makeTargetinDefine ends with makeIdent, makeSpecTarget or
makeComment, the following line is also matched as makeTargetinDefine.

So, add keepend to prevent that just as makeTarget does.

related: #18403
closes: #18570

Signed-off-by: Yiyang Wu <xgreenlandforwyy@gmail.com>
Signed-off-by: Roland Hieber <rohieb+vim-iR0jGdkV@rohieb.name>
Signed-off-by: Christian Brabandt <cb@256bit.org>