With leak sanitizer on, the test for getdelim fails due to a memory leak.

The attached patch fixes it. (Please feel free to amend.)

Regards, Tim

Output from config.log:

configure:26259: checking for working getdelim function
configure:26325: gcc-10 -o conftest -O1 -g -fno-omit-frame-pointer
-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize
=undefined,bool,alignment,null,enum,address,leak,nonnull-attribute
-fno-sanitize-recover=all -fsanitize-address-use-afte
r-scope   conftest.c  >&5
configure:26325: $? = 0
configure:26325: ./conftest

=================================================================
==551573==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 120 byte(s) in 1 object(s) allocated from:
    #0 0x7fb818f56e8f in malloc
(/usr/lib/x86_64-linux-gnu/libasan.so.6+0xa9e8f)
    #1 0x7fb8183f51bf in _IO_getdelim
/build/glibc-WZtAaN/glibc-2.30/libio/iogetdelim.c:62
    #2 0x7fb8198dd72f  (<unknown module>)

SUMMARY: AddressSanitizer: 120 byte(s) leaked in 1 allocation(s).
configure:26325: $? = 1
configure: program exited with status 1