Do not look at local headers when determining features

Avoids the detection of X11 on the build machine

build-scripts/cmake-toolchain-qnx-aarch64le.cmake

@@ -8,3 +8,7 @@ set(CMAKE_CXX_COMPILER q++)
 set(CMAKE_CXX_COMPILER_TARGET ${arch})
 
 set(CMAKE_SYSROOT $ENV{QNX_TARGET})
+
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)

build-scripts/cmake-toolchain-qnx-x86_64.cmake

@@ -8,3 +8,7 @@ set(CMAKE_CXX_COMPILER q++)
 set(CMAKE_CXX_COMPILER_TARGET ${arch})
 
 set(CMAKE_SYSROOT $ENV{QNX_TARGET})
+
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)