When building JDK 10 with extra link flags like so:

$ configure --with-extra-ldflags="...."

The extra link flags are not being passed to the command when libjsig.so is being linked.

Example:
$ configure --with-extra-ldflags="-Xlinker -z -Xlinker defs"

Then in build.log I see this:

[...]
Linking libjsig.so
( /usr/bin/gcc -Wl,--hash-style=both -Wl,-z,noexecstack -shared -m64 -o /disk/openjdk/upstream-sources/openjdk-10u/build/linux-x86_64-normal-server-release/support/modules_libs/java.base/libjsig.so /disk/openjdk/upstream-sources/openjdk-10u/build/linux-x86_64-normal-server-release/hotspot/libjsig/objs/jsig.o -ldl
[...]

Note that no "-Xlinker -z -Xlinker defs" flags are being passed.

This is not reproducible on JDK 11.