emulators/rpcs3: unbreak build after d458041ef5aa

• Checking for module 'pugixml>=1.15'
• Package dependency requirement 'pugixml >= 1.15' could not be satisfied.

Package 'pugixml' has version '1.14', required version is '>= 1.15'
CMake Error at /usr/local/share/cmake/Modules/FindPkgConfig.cmake:645 (message):

The following required packages were not found:

 - pugixml>=1.15

Reported by: pkg-fallout
(direct commit to 2025Q1 as bbc08dcb46a3 is missing on the branch)