databases/mysql80-server: fix build of client on powerpc

On powerpc, clang miscompiles comp_err, which later fails at runtime with:
->  0x102ff48c <+16>: .long  0x0006ee74                ; unknown opcode
The problem happens because of line:
frame #0: 0x10323eb4 comp_err`set_my_errno(my_errno=-10608) at my_thr_init.cc:344:47

GCC can compile client, but without -malign-double. It also needs to link to
libatomic (so building without GCC installed wouldn't work anyway).

This only fixes client. Server still fails to build because of:
/wrkdirs/usr/ports/databases/mysql80-server/work/mysql-8.0.32/storage/innobase/include/log0sys.h:190:60: error: static assertion failed
  190 |   static_assert(decltype(write_to_file_requests_interval)::is_always_lock_free);

databases/mysql80-server/Makefile

@@ -15,8 +15,8 @@ LICENSE=		GPLv2
 WRKSRC=		${WRKDIR}/${PORTNAME}-${PORTVERSION}${DISTVERSIONSUFFIX}
 
 SLAVEDIRS=	databases/mysql80-client
-USES=		bison:build cmake:noninja compiler:c++17-lang cpe \
-		groff:run libedit localbase ncurses perl5 pkgconfig shebangfix ssl
+USES=		bison:build cmake:noninja cpe groff:run libedit localbase \
+		ncurses perl5 pkgconfig shebangfix ssl
 
 CPE_VENDOR=	oracle
 
@@ -53,7 +53,7 @@ BUILD_DEPENDS_powerpc64=	libunwind>0:devel/libunwind
 BUILD_DEPENDS_powerpc64le=	libunwind>0:devel/libunwind
 
 CMAKE_BUILD_TYPE=	Release
-CFLAGS+=		-fPIC -malign-double
+CFLAGS+=		-fPIC
 CFLAGS_aarch64?=	-march=armv8-a+crc+crypto
 
 CMAKE_ARGS+=	-DINSTALL_LAYOUT=FREEBSD \
@@ -184,6 +184,14 @@ FEDERATED_SUB_LIST_OFF+=	FEDER=""
 SSP_UNSAFE=	yes
 .endif
 
+.if ${ARCH} == powerpc
+LDFLAGS+=	-latomic
+USES+=		compiler:gcc-c++11-lib
+.else
+CXXFLAGS+=	-malign-double
+USES+=		compiler:c++17-lang
+.endif
+
 post-extract:
 	@${RM} -rv ${WRKSRC}/sql/sql_hints.yy.cc ${WRKSRC}/sql/sql_hints.yy.h