Change ald to assemble successfully and include it in build.

While the scan of src/cmd/als.s clearly refers to ferror,
that routine is entirely missing from the scans of ald.

There are two identical ferror routines in src/cmd/adm.s and
src/cmd/apr.s printing the file name of a file that cannot be
openend.

ald calls ferror when unable to create a file. For ald to have
a similar ferror routine when creation fails appears sensible.

Therefore a similar routine is added to src/cmd/ald.s with
modifications to the variable containing the file name and
the label ferror jumps back to once done.

build/Makefile

@@ -112,6 +112,7 @@ dirs:
 # PLEASE KEEP IN ALPHABETICAL ORDER!
 cmd:	dirs \
 	$(BINDIR)/adm \
+	$(BINDIR)/ald \
 	$(BINDIR)/apr \
 	$(BINDIR)/as \
 	$(BINDIR)/cas \
@@ -152,6 +153,9 @@ altcmd: dirs cmd \
 $(BINDIR)/adm: $(CMDSRC)/adm.s
 	$(AS) $(ASARGS) -o $(BINDIR)/adm $(CMDSRC)/adm.s
 
+$(BINDIR)/ald: $(CMDSRC)/ald.s
+	$(AS) $(ASARGS) -o $(BINDIR)/ald $(CMDSRC)/ald.s
+
 $(BINDIR)/apr: $(CMDSRC)/apr.s
 	$(AS) $(ASARGS) -o $(BINDIR)/apr $(CMDSRC)/apr.s