Allow LD_PRELOAD libs to be configured at build time

Signed-off-by: Ikey Doherty <ikey@solus-project.com>

configure.ac

@@ -57,6 +57,13 @@ AC_SUBST(STEAMBIN)
 AC_DEFINE_UNQUOTED(STEAM_BINARY, "$STEAMBIN",
                    [The location of the real Steam binary])
 
+# The LD_PRELOAD list required to integrate gracefully with the official Steam Runtime
+AC_ARG_WITH([preload-libs], AS_HELP_STRING([--with-preload-libs],
+        [the preload libs to use with Steams own runtime]), [preloadlibs="${withval}"],
+        [preloadlibs="/usr/\$LIB/libX11.so.6:/usr/\$LIB/libstdc++.so.6"])
+
+AC_DEFINE_UNQUOTED([LSI_PRELOAD_LIBS], "$preloadlibs",
+                   [Libraries to preload with Steams runtime])
 
 m4_define([gtk_required_version], [3.4.0])
 
@@ -88,6 +95,7 @@ AC_MSG_RESULT([
         New C++ ABI:            ${use_new_abi}
         Real Steam binary:      ${STEAMBIN}
         GTK+ Frontend:          ${have_frontend}
+        preload-libs:           ${preloadlibs}
 
         compiler:               ${CC}
         cflags:                 ${CFLAGS}

src/shim/lsi.h

@@ -19,6 +19,8 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include "config.h"
+
 /* Mark a variable/argument as unused to skip warnings */
 #define __lsi_unused__ __attribute__((unused))
 
@@ -86,7 +88,11 @@ __lsi_inline__ static inline bool lsi_system_requires_preload(void)
  */
 __lsi_inline__ static inline const char *lsi_preload_list(void)
 {
-        return "/usr/$LIB/libX11.so.6:/usr/$LIB/libstdc++.so.6";
+        /* Respect existing LD_PRELOAD in environment */
+        if (getenv("LD_PRELOAD")) {
+                return "$LD_PRELOAD:" LSI_PRELOAD_LIBS;
+        }
+        return LSI_PRELOAD_LIBS;
 }
 
 /**