ci: disable pch for tidy/iwyu builds

PCH is incompabible with iwyu:
  error: include-what-you-use does not support PCH

It seems likely that it'd mess with clang-tidy as well.

ci/test/03_test_script.sh

@@ -122,7 +122,7 @@ cd "${BASE_BUILD_DIR}"
 BITCOIN_CONFIG_ALL="$BITCOIN_CONFIG_ALL -DENABLE_EXTERNAL_SIGNER=ON -DCMAKE_INSTALL_PREFIX=$BASE_OUTDIR"
 
 if [[ "${RUN_TIDY}" == "true" ]]; then
-  BITCOIN_CONFIG_ALL="$BITCOIN_CONFIG_ALL -DCMAKE_EXPORT_COMPILE_COMMANDS=ON"
+  BITCOIN_CONFIG_ALL="$BITCOIN_CONFIG_ALL -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_DISABLE_PRECOMPILE_HEADERS=ON"
 fi
 
 bash -c "cmake -S $BASE_ROOT_DIR $BITCOIN_CONFIG_ALL $BITCOIN_CONFIG || ( (cat $(cmake -P "${BASE_ROOT_DIR}/ci/test/GetCMakeLogFiles.cmake")) && false)"