Merge bitcoin#28875: build: Pass sanitize flags to instrument libsecp256k1 code

cbea49c build: Pass sanitize flags to instrument `libsecp256k1` code (Hennadii Stepanov)

Pull request description:

  This PR is a revived bitcoin#27991 with an addressed [comment](bitcoin#27991 (comment)).

  Fixes bitcoin#27990.

  Might be tested as follows:
  ```
  $ ./autogen.sh && ./configure --enable-fuzz --with-sanitizers=fuzzer CC=clang-13 CXX=clang++-13
  $ make clean > /dev/null && make
  $ objdump --disassemble=secp256k1_xonly_pubkey_serialize src/test/fuzz/fuzz | grep __sanitizer_cov
   1953bd0:e8 bb c6 05 ff       call   9b0290 <__sanitizer_cov_trace_const_cmp8>
   1953d32:e8 69 c4 05 ff       call   9b01a0 <__sanitizer_cov_trace_pc_indir>
   1953d58:e8 43 c4 05 ff       call   9b01a0 <__sanitizer_cov_trace_pc_indir>
   1953d82:e8 19 c4 05 ff       call   9b01a0 <__sanitizer_cov_trace_pc_indir>
  ```

ACKs for top commit:
  fanquake:
    ACK cbea49c
  dergoegge:
    reACK cbea49c

Tree-SHA512: 801994e75b711d20eaf0d675f378da07d693f4a7de026efd93860f5f1deabed855a83eca3561725263e4fe605fcc5f91eb73c021ec91c831864e6deb575e3885

Author: fanquake

configure.ac

@@ -381,7 +381,8 @@ if test "$use_sanitizers" != ""; then
   dnl fail if a bad argument is passed, e.g. -fsanitize=undfeined
   AX_CHECK_COMPILE_FLAG(
     [-fsanitize=$use_sanitizers],
-    [SANITIZER_CXXFLAGS="-fsanitize=$use_sanitizers"],
+    [SANITIZER_CXXFLAGS="-fsanitize=$use_sanitizers"
+     SANITIZER_CFLAGS="-fsanitize=$use_sanitizers"],
     [AC_MSG_ERROR([compiler did not accept requested flags])])
 
   dnl Some compilers (e.g. GCC) require additional libraries like libasan,
@@ -1931,6 +1932,9 @@ CPPFLAGS_TEMP="$CPPFLAGS"
 unset CPPFLAGS
 CPPFLAGS="$CPPFLAGS_TEMP"
 
+if test -n "$use_sanitizers"; then
+  export SECP_CFLAGS="$SECP_CFLAGS $SANITIZER_CFLAGS"
+fi
 ac_configure_args="${ac_configure_args} --disable-shared --with-pic --enable-benchmark=no --enable-module-recovery --disable-module-ecdh"
 AC_CONFIG_SUBDIRS([src/secp256k1])
 
@@ -1990,7 +1994,7 @@ echo "  target os       = $host_os"
 echo "  build os        = $build_os"
 echo
 echo "  CC              = $CC"
-echo "  CFLAGS          = $PTHREAD_CFLAGS $CFLAGS"
+echo "  CFLAGS          = $PTHREAD_CFLAGS $SANITIZER_CFLAGS $CFLAGS"
 echo "  CPPFLAGS        = $DEBUG_CPPFLAGS $HARDENED_CPPFLAGS $CORE_CPPFLAGS $CPPFLAGS"
 echo "  CXX             = $CXX"
 echo "  CXXFLAGS        = $CORE_CXXFLAGS $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $SANITIZER_CXXFLAGS $CXXFLAGS"

test/sanitizer_suppressions/ubsan

@@ -23,6 +23,7 @@ implicit-integer-sign-change:secp256k1/
 implicit-signed-integer-truncation:*/include/c++/
 implicit-signed-integer-truncation:leveldb/
 implicit-signed-integer-truncation:secp256k1/
+implicit-signed-integer-truncation,implicit-integer-sign-change:secp256k1_modinv64_posdivsteps_62_var
 implicit-unsigned-integer-truncation:*/include/c++/
 implicit-unsigned-integer-truncation:leveldb/
 implicit-unsigned-integer-truncation:secp256k1/