Disable dlsym hooking by default and fix LD_PRELOAD propagation to new processes

This allows `mangohud steam` to work

meson_options.txt

@@ -8,3 +8,4 @@ option('with_xnvctrl', type : 'feature', value : 'enabled', description: 'Enable
 option('with_x11', type : 'feature', value : 'enabled')
 option('with_wayland', type : 'feature', value : 'disabled')
 option('with_dbus', type : 'feature', value : 'enabled')
+option('with_dlsym', type : 'feature', value : 'disabled')

src/meson.build

@@ -63,7 +63,9 @@ opengl_files = files(
   'gl/inject_egl.cpp',
 )
 
-pre_args += '-DHOOK_DLSYM'
+if get_option('with_dlsym').enabled()
+    pre_args += '-DHOOK_DLSYM'
+endif
 
 if get_option('with_xnvctrl').enabled()
 

src/overlay.cpp

@@ -817,7 +817,10 @@ void init_gpu_stats(uint32_t& vendorID, overlay_params& params)
 }
 
 void init_system_info(){
-      unsetenv("LD_PRELOAD");
+      const char* ld_preload = getenv("LD_PRELOAD");
+      if (ld_preload)
+         unsetenv("LD_PRELOAD");
+
       ram =  exec("cat /proc/meminfo | grep 'MemTotal' | awk '{print $2}'");
       trim(ram);
       cpu =  exec("cat /proc/cpuinfo | grep 'model name' | tail -n1 | sed 's/^.*: //' | sed 's/([^)]*)/()/g' | tr -d '(/)'");
@@ -833,6 +836,8 @@ void init_system_info(){
       trim(driver);
       //driver = itox(device_data->properties.driverVersion);
 
+      if (ld_preload)
+         setenv("LD_PRELOAD", ld_preload, 1);
 #ifndef NDEBUG
       std::cout << "Ram:" << ram << "\n"
                 << "Cpu:" << cpu << "\n"