cross compile fail on arm/mips musl

*../libmysql/libmysqlclient.a(my_context.c.o): In function `my_context_spawn_internal':

my_context.c:(.text+0x3c): undefined reference to `setcontext'

my_context.c:(.text+0x40): undefined reference to `setcontext'

../libmysql/libmysqlclient.a(my_context.c.o): In function `my_context_continue':

my_context.c:(.text+0xa4): undefined reference to `swapcontext'

my_context.c:(.text+0xc4): undefined reference to `swapcontext'

../libmysql/libmysqlclient.a(my_context.c.o): In function `my_context_spawn':

my_context.c:(.text+0x140): undefined reference to `getcontext'

my_context.c:(.text+0x15c): undefined reference to `getcontext'

my_context.c:(.text+0x180): undefined reference to `makecontext'

my_context.c:(.text+0x1c0): undefined reference to `makecontext'

../libmysql/libmysqlclient.a(my_context.c.o): In function `my_context_yield':

my_context.c:(.text+0x204): undefined reference to `swapcontext'

my_context.c:(.text+0x218): undefined reference to `swapcontext'

collect2: error: ld returned 1 exit status*

@@ -31,8 +31,6 @@

 #define MY_CONTEXT_USE_X86_64_GCC_ASM

 #elif defined(__GNUC__) && __GNUC__ >= 3 && defined(__i386__)

 #define MY_CONTEXT_USE_I386_GCC_ASM

-#elif defined(HAVE_UCONTEXT_H)

-#define MY_CONTEXT_USE_UCONTEXT

 #else

 #define MY_CONTEXT_DISABLE

 #endif