doc: Add missing arm_arch_v8a_hard_ok anchor

2020-04-29  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* doc/sourcebuild.texi: Add missing arm_arch_v8a_hard_ok anchor.

gcc/ChangeLog

 2020-04-29  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* doc/sourcebuild.texi: Add missing arm_arch_v8a_hard_ok anchor.
+
+2020-04-29  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* config/arm/arm-builtins.c (arm_atomic_assign_expand_fenv): Use
 	TARGET_EXPR instead of MODIFY_EXPR for the first assignments to
 	fenv_var and new_fenv_var.

gcc/doc/sourcebuild.texi

@@ -1830,6 +1830,7 @@ ARM target supports @code{-mfpu=vfp3 -mfloat-abi=softfp}.
 Some multilibs may be incompatible with these options.
 
 @item arm_arch_v8a_hard_ok
+@anchor{arm_arch_v8a_hard_ok}
 The compiler is targeting @code{arm*-*-*} and can compile and assemble code
 using the options @code{-march=armv8-a -mfpu=neon-fp-armv8 -mfloat-abi=hard}.
 This is not enough to guarantee that linking works.