ldso: add lx_environ to symbol map

This symbol must be exported to build dynamically-linked executables on
the lx_hybrid_x86 base platform.

repos/base/src/lib/ldso/symbol.map

@@ -79,6 +79,9 @@
 		/* Linux */
 		lx_syscall;
 
+		/* Linux hybrid */
+		lx_environ;
+
 		/* Base HW */
 		extern "C++" {
 			Kernel::*;