If I try to build openjdk10 with clang-4.0 fastdebug on linux-x86_64, I see a crash:

# Internal Error (/home/martin/ws/jdk10-hs-clang-4.0/hotspot/src/os_cpu/linux_x86/vm/os_linux_x86.cpp:825), pid=638, tid=639
# assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0) failed: incorrect stack alignment
#
# JRE version: (10.0) (fastdebug build )
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 10-internal+0-adhoc.martin.jdk10-hs-clang-4.0, mixed mode, tiered, compressed oops, serial gc, linux-amd64)

Recipe:
bash ./configure --with-toolchain-type=clang --disable-warnings-as-errors --with-toolchain-path=/usr/lib/llvm-4.0/bin --with-extra-ldflags=-z execstack --disable-precompiled-headers --enable-unlimited-crypto --with-native-debug-symbols=none --with-default-make-target=jdk-image test-image --with-debug-level=fastdebug --with-boot-jdk=/home/martin/jdk/jdk9