bitcoin-core: disable _FORTIFY_SOURCE for MSAN (google#11792)

Related to bitcoin/bitcoin#29837.

Author: fanquake

projects/bitcoin-core/build.sh

@@ -54,7 +54,9 @@ sed -i "s|PROVIDE_FUZZ_MAIN_FUNCTION|NEVER_PROVIDE_MAIN_FOR_OSS_FUZZ|g" "./confi
 # * --enable-fuzz, see https://github.com/bitcoin/bitcoin/blob/master/doc/fuzzing.md
 # * CONFIG_SITE, see https://github.com/bitcoin/bitcoin/blob/master/depends/README.md
 if [ "$SANITIZER" = "memory" ]; then
-  CONFIG_SITE="$PWD/depends/$BUILD_TRIPLET/share/config.site" ./configure --enable-fuzz SANITIZER_LDFLAGS="$LIB_FUZZING_ENGINE" --disable-hardening
+  # _FORTIFY_SOURCE is not compatible with MSAN.
+  export CPPFLAGS="${CPPFLAGS} -U_FORTIFY_SOURCE"
+  CONFIG_SITE="$PWD/depends/$BUILD_TRIPLET/share/config.site" ./configure --enable-fuzz SANITIZER_LDFLAGS="$LIB_FUZZING_ENGINE"
 else
   CONFIG_SITE="$PWD/depends/$BUILD_TRIPLET/share/config.site" ./configure --enable-fuzz SANITIZER_LDFLAGS="$LIB_FUZZING_ENGINE"
 fi