configure.ac: fix for upcoming autoconf-2.70

The failure initially noticed on `autoconf-2.69d` (soon to become 2.70):

```
$ ./configure
./configure: line 8720: syntax error near unexpected token `fi'
./configure: line 8720: `fi'
```

Before the change generated `./configure ` snippet looked like:

```
    if ! $CC -E -xc - <<SRC >/dev/null
then :

	#if defined __APPLE_CC__ && defined __clang_major__ && __clang_major__ < 3
	#error premature clang
	#endif
SRC
	as_fn_error $? "clang version 3.0 or later is required" "$LINENO" 5
fi
```

Note the newline that breaks here-document syntax.

After the change the snippet does not use here-document.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

0 files changed, 0 insertions, 0 deletions