Persistent kernel build trouble on RPi3

[bob prohaska]

Recent attempts to compile a kernel on -current running on an RPi3 have 
been failing through r331541. The persistent error message is:

--- all_subdir_armv8crypto ---
In file included from /usr/src/sys/crypto/armv8/armv8_crypto_wrap.c:46:
In file included from /usr/lib/clang/6.0.0/include/arm_neon.h:31:
/usr/lib/clang/6.0.0/include/stdint.h:228:25: error: typedef redefinition with different types ('int16_t' (aka 'short') vs '__int_fast16_t' (aka 'int'))
typedef __int_least16_t int_fast16_t;
                        ^
/usr/src/sys/sys/stdint.h:51:25: note: previous definition is here
typedef __int_fast16_t          int_fast16_t;
                                ^
In file included from /usr/src/sys/crypto/armv8/armv8_crypto_wrap.c:46:
In file included from /usr/lib/clang/6.0.0/include/arm_neon.h:31:
/usr/lib/clang/6.0.0/include/stdint.h:229:26: error: typedef redefinition with different types ('uint16_t' (aka 'unsigned short') vs '__uint_fast16_t' (aka 'unsigned int'))
typedef __uint_least16_t uint_fast16_t;
                         ^
/usr/src/sys/sys/stdint.h:56:26: note: previous definition is here
typedef __uint_fast16_t         uint_fast16_t;
                                ^
In file included from /usr/src/sys/crypto/armv8/armv8_crypto_wrap.c:46:
In file included from /usr/lib/clang/6.0.0/include/arm_neon.h:31:
/usr/lib/clang/6.0.0/include/stdint.h:245:24: error: typedef redefinition with different types ('int8_t' (aka 'signed char') vs '__int_fast8_t' (aka 'int'))

Repeated attempts to update source haven't cleared the error, including
complete replacement checkout.

Any guidance would be appreciated.

Thanks for reading,

bob prohaska