app/spdk_top: fix ncurses link flags

Fixes #3647

The ncurses library depends on libtinfo.
One some Linux distributions, this dependency cannot be resolved
correctly when just linking agains libncurses.
Both libraries have to be linked against separately in that case, which is
currently not done in app/spdk_top.

Since this problem is distribution-specific, this patch uses `pkg-config`
to automatically determine whether libncurses requires the additional
linker flag for libtinfo or not.

Change-Id: Ib4d234cc432d3f6fdec15e58bfccfb8f840ee935
Signed-off-by: Anton Einax <butterino@proton.me>
Reviewed-on: https://review.spdk.io/c/spdk/spdk/+/25816


Reviewed-by: Jim Harris <jim.harris@nvidia.com>
Reviewed-by: Changpeng Liu <changpeliu@tencent.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK Automated Test System <spdkbot@gmail.com>
Reviewed-by: Aleksey Marchuk <alexeymar@nvidia.com>