vtk: Fix builds for 10.6

[Dave-Allured]

Description

Disable broken patch for 10.6 only; one hunk only.
Attempt to progress broken builds for 10.6.

Type(s)

• bugfix

Tested on

CI only.
Waiting for merge to check 10.6 builders.

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[Dave-Allured]

Result: This got us past the patch error. It looks like upstream changed the method of linking to X11 or OpenGL.

However, this now returns us to the previous build error on 10.6:

cd /opt/local/var/macports/build/vtk-c7880540/work/build/ThirdParty/kissfft/vtkkissfft && /opt/local/bin/clang-mp-11 -Dkiss_fft_scalar=double -Dkissfft_EXPORTS -I/opt/local/var/macports/build/vtk-c7880540/work/vtk-9.6.1/ThirdParty/kissfft/vtkkissfft -I/opt/local/var/macports/build/vtk-c7880540/work/build/ThirdParty/kissfft/vtkkissfft -isystem /opt/local/var/macports/build/vtk-c7880540/work/build/ThirdParty/kissfft -isystem /opt/local/var/macports/build/vtk-c7880540/work/vtk-9.6.1/ThirdParty/kissfft -pipe -Os -DNDEBUG -isystem/opt/local/include/libcxx/v1 -nostdinc++ -isystem/opt/local/include/LegacySupport -I/opt/local/include  -O3 -DNDEBUG -arch x86_64 -mmacosx-version-min=10.6 -fPIC -MD -MT ThirdParty/kissfft/vtkkissfft/CMakeFiles/kissfft.dir/kiss_fft.c.o -MF CMakeFiles/kissfft.dir/kiss_fft.c.o.d -o CMakeFiles/kissfft.dir/kiss_fft.c.o -c /opt/local/var/macports/build/vtk-c7880540/work/vtk-9.6.1/ThirdParty/kissfft/vtkkissfft/kiss_fft.c
In file included from /opt/local/var/macports/build/vtk-c7880540/work/vtk-9.6.1/ThirdParty/kissfft/vtkkissfft/kiss_fft.c:10:
In file included from /opt/local/var/macports/build/vtk-c7880540/work/vtk-9.6.1/ThirdParty/kissfft/vtkkissfft/_kiss_fft_guts.h:13:
In file included from /opt/local/var/macports/build/vtk-c7880540/work/vtk-9.6.1/ThirdParty/kissfft/vtkkissfft/kiss_fft.h:14:
/opt/local/include/libcxx/v1/math.h:316:8: error: expected identifier or '('
extern "C" {
       ^

I think this might be the C++ flags mixup that was discussed elsewhere, but not sure. Let us keep this commit as a step in the right direction.