parisc: Makefile: explain that 64BIT requires both 32-bit and 64-bit compilers

For building a 64-bit kernel, both 32-bit and 64-bit VDSO binaries
are built, so both 32-bit and 64-bit compilers (and tools) should be
in the PATH environment variable.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v5.3+

Author: rddunlap

arch/parisc/Makefile

@@ -39,7 +39,9 @@ endif
 
 export LD_BFD
 
-# Set default 32 bits cross compilers for vdso
+# Set default 32 bits cross compilers for vdso.
+# This means that for 64BIT, both the 64-bit tools and the 32-bit tools
+# need to be in the path.
 CC_ARCHES_32 = hppa hppa2.0 hppa1.1
 CC_SUFFIXES  = linux linux-gnu unknown-linux-gnu suse-linux
 CROSS32_COMPILE := $(call cc-cross-prefix, \