build: use valgrind client request to detect undefined memory use

This tightens the check introduced in
ac2f71b8, by using the valgrind client
request to explicitly mark the "uninitialized but initialization is
needed before use" regions.  With this patch and the
fix (c01011c2) reverted, you will see
the following error when running dtls_hello_random_value under
valgrind:

  $ valgrind ./dtls_hello_random_value
  testing: default
  ==520145== Conditional jump or move depends on uninitialised value(s)
  ==520145==    at 0x4025F5: hello_callback (dtls_hello_random_value.c:90)
  ==520145==    by 0x488BF97: _gnutls_call_hook_func (handshake.c:1215)
  ==520145==    by 0x488C1AA: _gnutls_send_handshake2 (handshake.c:1332)
  ==520145==    by 0x488FC7E: send_client_hello (handshake.c:2290)
  ==520145==    by 0x48902A1: handshake_client (handshake.c:2908)
  ==520145==    by 0x48902A1: gnutls_handshake (handshake.c:2740)
  ==520145==    by 0x402CB3: client (dtls_hello_random_value.c:153)
  ==520145==    by 0x402CB3: start (dtls_hello_random_value.c:317)
  ==520145==    by 0x402EFE: doit (dtls_hello_random_value.c:331)
  ==520145==    by 0x4023D4: main (utils.c:254)
  ==520145==

Signed-off-by: Daiki Ueno <[email protected]>
21 jobs for tmp-valgrind-memcheck in 74 minutes and 47 seconds (queued for 1 second)
Status Job ID Name Coverage
  Stage1 Testing
passed #492701313
linux docker shared
Debian.cross.aarch64-linux-gnu

01:09:10

passed #492701308
linux docker shared
Debian.cross.arm-linux-gnueabihf

01:14:43

passed #492701304
linux docker shared
Debian.cross.i686-linux-gnu

00:30:55

passed #492701309
linux docker shared
Debian.cross.mips-linux-gnu

01:06:42

passed #492701303
linux shared
Debian.x86_64

00:26:05

passed #492701289
linux shared
FIPS140-2.Fedora.x86_64

00:25:57

passed #492701300
freebsd
FreeBSD.x86_64

00:33:46

passed #492701299
linux docker shared
MinGW32

00:28:45

passed #492701298
linux docker shared
MinGW64

00:24:12

passed #492701287
linux shared
SSL-3.0.Fedora.x86_64

00:27:55

passed #492701302
linux shared
UB+ASAN-Werror.Fedora.x86_64.gcc

00:43:58

passed #492701283
linux shared
abi/coverage

00:30:15

76.8%
passed #492701278
commit-check

00:00:52

passed #492701280
linux shared
doc-dist.Fedora

00:46:19

passed #492701286
linux shared
minimal.Fedora.x86_64

00:21:14

passed #492701315
linux shared
nettle-master.Fedora

00:29:45

passed #492701296
linux shared
static-analyzers.Fedora.x86_64

00:26:45

passed #492701294
linux shared
threadsan.Fedora.x86_64

00:12:11

passed #492701293
linux shared
valgrind.Fedora.x86_64

01:01:58

 
  External
passed LGTM analysis: C/C++

00:23:31

passed LGTM analysis: JavaScript

00:04:10