graphics/poppler: ignore graphics/openjpeg15 presence

• cmake can under some non-determinstic circumstances find the OpenJPEGConfig.cmake in

${PREFIX}/lib/openjpeg-1.5

prior to the one in

${PREFIX}/lib/openjpeg2

with would be the wanted one.

• Use CMAKE_IGNORE_PATH to explicitely make it not see that prefix. https://cmake.org/cmake/help/latest/variable/CMAKE_IGNORE_PATH.html#variable:CMAKE_IGNORE_PATH

PR: 262888