Add back optval dependencies accidentally removed in merge conflict resolution

Author: ghbrown

src/Makefile.manual

@@ -88,8 +88,9 @@ stdlib_io.o: \
     stdlib_kinds.o \
     stdlib_ascii.o
 stdlib_linalg.o: \
+	stdlib_error.o \
 	stdlib_kinds.o \
-	stdlib_error.o
+	stdlib_optval.o
 stdlib_linalg_diag.o: \
     stdlib_linalg.o \
     stdlib_kinds.o

src/stdlib_linalg.fypp

@@ -6,6 +6,7 @@ module stdlib_linalg
   use stdlib_kinds, only: sp, dp, qp, &
     int8, int16, int32, int64
   use stdlib_error, only: error_stop
+  use stdlib_optval, only: optval
   implicit none
   private