I tried LDFLAGS=-lposix4 and LDFLAGS=-lrt, both yielded the same result:

ld.so.1: t-version: fatal: relocation error: file t-version: symbol
gpg_error_check_version: referenced symbol not found
/bin/bash: line 5: 18688 Killed ${dir}$tst
FAIL: t-version
Unspecified source: Success
gcrypt: Invalid length specifier in S-expression
GnuPG: Unknown packet
GpgSM: Certificate too young
GPG Agent: Bad CA certificate
Pinentry: Operation cancelled
SCD: Card removed
GPGME: Bad secret key
Keybox: Unknown error code
PASS: t-strerror
ld.so.1: t-syserror: fatal: relocation error: file t-syserror: symbol
gpg_err_code_from_syserror: referenced symbol not found
/bin/bash: line 5: 18696 Killed ${dir}$tst
FAIL: t-syserror
ld.so.1: t-lock: fatal: relocation error: file t-lock: symbol
gpg_error_check_version: referenced symbol not found
/bin/bash: line 5: 18701 Killed ${dir}$tst
FAIL: t-lock
ld.so.1: t-printf: fatal: relocation error: file t-printf: symbol
gpg_error_check_version: referenced symbol not found
/bin/bash: line 5: 18706 Killed ${dir}$tst
FAIL: t-printf
ld.so.1: t-poll: fatal: relocation error: file t-poll: symbol
gpg_error_check_version: referenced symbol not found
/bin/bash: line 5: 18711 Killed ${dir}$tst

FAIL: t-poll

5 of 6 tests failed

Please report to http://bugs.gnupg.org

Makefile:564: recipe for target 'check-TESTS' failed
make[2]: * [check-TESTS] Error 1
make[2]: Leaving directory '/home/alelai/libgpg-error-1.21.src/tests'
Makefile:687: recipe for target 'check-am' failed
make[1]: * [check-am] Error 2
make[1]: Leaving directory '/home/alelai/libgpg-error-1.21.src/tests'
Makefile:471: recipe for target 'check-recursive' failed
make: *** [check-recursive] Error 1