"make" skips files that had build failure on next run

[W. J. van der Laan]

Hello,

I think there is a slight bug in the build system: when a build for a 
compilation unit fails due to an error, the next time "make" is run, when not 
touching the source file in question, it skips that file:

$ make
⋮
  CC         ../lib/stdlib/atol.c
atol.s:5 :Received invalid other; push___%ra
mescc: failed: /data/src/mescc-tools/bin/M1 --LittleEndian --architecture 
riscv64 -f ../lib/riscv64-mes/riscv64.M1 -f atol.s -o atol.o
$ cat atol.o
<
:atol
$ make
⋮
  AR         libc+tcc.a
  CC         ../lib/stdlib/mbstowcs.c
⋮
$ cat

It seems that partial output is generated, and confused for a successfully 
built file. Not a big deal when bootstrapping but it can lead to confusion 
during development.

-W