[doc] Add missing documentation for existing target checks

gcc/ChangeLog:
2020-01-07  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* doc/sourcebuild.texi (arm_little_endian, arm_nothumb): Documented
	existing target checks.

From-SVN: r279957

gcc/ChangeLog

+2020-01-07  Andre Vieira  <andre.simoesdiasvieira@arm.com>
+
+	* doc/sourcebuild.texi (arm_little_endian, arm_nothumb): Documented
+	existing target checks.
+
 2020-01-07  Richard Biener  <rguenther@suse.de>
 
 	* doc/install.texi: Bump minimal supported MPC version.

gcc/doc/sourcebuild.texi

@@ -1721,6 +1721,9 @@ Target generates decimal floating point instructions with current options.
 @item arm32
 ARM target generates 32-bit code.
 
+@item arm_little_endian
+ARM target that generates little-endian code.
+
 @item arm_eabi
 ARM target adheres to the ABI for the ARM Architecture.
 
@@ -1808,6 +1811,9 @@ ARM target generates Thumb-1 code for @code{-mthumb}.
 @item arm_thumb2_ok
 ARM target generates Thumb-2 code for @code{-mthumb}.
 
+@item arm_nothumb
+ARM target that is not using Thumb.
+
 @item arm_vfp_ok
 ARM target supports @code{-mfpu=vfp -mfloat-abi=softfp}.
 Some multilibs may be incompatible with these options.