ldso: Make truly self relocatable

On Linux the linker can now be loaded at arbitrary addresses, this became
necessary for newer kernel versions. The 'linux_arm' target is not supported.

Issue #1728

repos/base-linux/src/lib/lx_hybrid/lx_hybrid.cc

@@ -19,6 +19,12 @@
 
 extern "C" int raw_write_str(const char *str);
 
+/**
+ * Define context area
+ */
+Genode::addr_t _context_area_start;
+
+
 enum { verbose_atexit = false };