(autoconf.info)Failure in Make Rules

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11.2 Failure in Make Rules

Since 1992 Posix has required that `make' must invoke each command with
the equivalent of a `sh -c' subshell.  However, many `make'
implementations, including BSD make through 2004, use `sh -e -c'
instead, and the `-e' option causes the subshell to exit immediately if
a subsidiary simple-command fails.  For example, the command `touch T;
rm -f U' always attempts to remove `U' with Posix make, but incompatible
`make' implementations skip the `rm' if the `touch' fails.  One way to
work around this is to reword the affected simple-commands so that they
always succeed, e.g., `touch T || :; rm -f U'.  However, even this
approach can run into common bugs in BSD implementations of the `-e'
option of `sh' and `set' (Note: Limitations of Builtins), so if you
are worried about porting to buggy BSD shells it may be simpler to
migrate complicated `make' actions into separate scripts.

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