add /usr/lib to default search path for the dynamic linker

--- a/libc/Makeconfig
+++ b/libc/Makeconfig
@@ -539,6 +539,9 @@
 default-rpath = $(libdir)
 endif
 
+# Add /usr/lib to default search path for the dynamic linker
+user-defined-trusted-dirs := /usr/lib
+
 ifndef link-extra-libs
 link-extra-libs = $(LDLIBS-$(@F))
 link-extra-libs-static = $(link-extra-libs)