ci: fix gcc unit tests script

tools/ci/amd64/gcc/unit_tests.sh

@@ -4,13 +4,27 @@ set -e
 cd $(git rev-parse --show-toplevel)/
 rm -rf ./build
 
-conan build . \
-  -c tools.system.package_manager:mode=install \
-  -c tools.cmake.cmaketoolchain:generator=Ninja \
-  -s build_type=Release \
-  -o enable_unit_tests=True \
-  -o use_mold=True \
-  --build=missing
+Xvfb :99 -screen 0 1024x768x16 &
+export DISPLAY=:99
+export CXX=$(which g++)
+export CC=$(which gcc)
+
+conan conan build . \
+    -c tools.system.package_manager:mode=install \
+    -c tools.cmake.cmaketoolchain:generator=Ninja \
+    -c tools.build:compiler_executables='{"c": "gcc", "cpp": "g++"}' \
+    -s build_type=Release \
+    -s compiler=gcc \
+    -s compiler.version=15 \
+    -s compiler.libcxx=libstdc++ \
+    -o use_mold=True \
+    -o enable_unit_tests=True \
+    -o enable_fuzz_tests=False \
+    -o enable_llvm_coverage=False \
+    -o enable_static_analysis=False \
+    -o use_mold=True \
+    -o export_compile_commands=False \
+    --build=missing
 
 for test in $(find ./build -type f -name '*_tests' -executable); do
   echo "Running $test"