Avoid building dependent ports of FLTK on x64-linux (#53144)

scripts/ci.feature.baseline.txt

@@ -744,6 +744,7 @@ mapnik[viewer]:arm64-linux=cascade
 materialx[render]:arm64-linux=feature-fails
 mathgl[arma]:arm64-linux=cascade
 mathgl[fltk]:arm64-linux=cascade
+mathgl[fltk]:x64-linux=skip  # Xft linking issue https://github.com/microsoft/vcpkg/issues/52825
 mathgl[glut]:arm64-linux=cascade
 mathgl[hdf5,qt5]:arm64-windows=cascade
 mathgl[opengl]:arm64-linux=feature-fails
@@ -823,6 +824,7 @@ nvtt[cuda]:x86-windows=cascade
 nvtt[cuda](x64 & (linux | windows))=feature-fails  # nvtt getting dated wrt cuda
 octave:arm64-linux=fail
 octave:arm64-osx=fail  # blas must select openblas instead of Accelerate
+octave[fltk]:x64-linux=skip  # Xft linking issue https://github.com/microsoft/vcpkg/issues/52825
 octave(android)=skip
 ode:arm64-windows=fail
 ogdf:arm64-linux=fail

scripts/test_ports/vcpkg-ci-mathgl/vcpkg.json

@@ -9,7 +9,10 @@
       "features": [
         "arma",
         "examples",
-        "fltk",
+        {
+          "name": "fltk",
+          "platform": "!(x64 & linux)"
+        },
         "gif",
         "glut",
         "gsl",

scripts/test_ports/vcpkg-ci-octave/vcpkg.json

@@ -15,7 +15,10 @@
         "colamd",
         "curl",
         "cxsparse",
-        "fltk",
+        {
+          "name": "fltk",
+          "platform": "!(x64 & linux)"
+        },
         "fontconfig",
         "freetype",
         "graphicsmagick",