toolchain-external: add fortran support option for custom external toolchains

If a custom external toolchain is used, we can't enable the fortran
support. Add a new option for that.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

toolchain/toolchain-external/toolchain-external-custom/Config.in.options

@@ -405,6 +405,14 @@ config BR2_TOOLCHAIN_EXTERNAL_CXX
 	  support. If you don't know, leave the default value,
 	  Buildroot will tell you if it's correct or not.
 
+config BR2_TOOLCHAIN_EXTERNAL_FORTRAN
+	bool "Toolchain has Fortran support?"
+	select BR2_TOOLCHAIN_HAS_FORTRAN
+	help
+	  Select this option if your external toolchain has Fortran
+	  support. If you don't know, leave the default value,
+	  Buildroot will tell you if it's correct or not.
+
 config BR2_TOOLCHAIN_EXTRA_EXTERNAL_LIBS
 	string "Extra toolchain libraries to be copied to target"
 	help