scripts/sorttable: riscv: fix undeclared identifier 'EM_RISCV' error

Fix the following build failure reported in [1] by adding a conditional
definition of EM_RISCV in order to allow cross-compilation on machines
which do not have EM_RISCV definition in their host.

   scripts/sorttable.c:352:7: error: use of undeclared identifier 'EM_RISCV'

EM_RISCV was added to <elf.h> in glibc 2.24 so builds on systems with
glibc headers < 2.24 should show this error.

[[email protected]: changelog addition]
Link: https://lore.kernel.org/lkml/[email protected]/ [1]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 54fed35 ("riscv: Enable BUILDTIME_TABLE_SORT")
Signed-off-by: Miles Chen <[email protected]>
Reported-by: Stefan Wahren <[email protected]>
Tested-by: Stefan Wahren <[email protected]>
Reviewed-by: Jisheng Zhang <[email protected]>
Cc: Michal Kubecek <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Markus Mayer <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: milesdotchen

scripts/sorttable.c

@@ -54,6 +54,10 @@
 #define EM_ARCV2	195
 #endif
 
+#ifndef EM_RISCV
+#define EM_RISCV	243
+#endif
+
 static uint32_t (*r)(const uint32_t *);
 static uint16_t (*r2)(const uint16_t *);
 static uint64_t (*r8)(const uint64_t *);