RISC-V: Add path of library directories for the 32-bit

For the recommand of 64 bit version, we add the libraries path of 32 bit
in this patch.

The status of RV32 binaries under RV64 kernels is that the ISA
optionally supports having different XLEN for user and supervisor modes,
but AFAIK there's no silicon that implements this feature, and the Linux
kernel doesn't support it yet.

For the recommand of 64 bit version, we add the libraries path of 32 bit
in this patch. This includes a fix to avoid an out of bound array check
when building with GCC 8.2.

sysdeps/unix/sysv/linux/riscv/dl-cache.h

@@ -34,6 +34,8 @@
    RISC-V, libraries can be found in paths ending in:
      - /lib64/lp64d
      - /lib64/lp64
+     - /lib32/ilp32d
+     - /lib32/ilp32
      - /lib (only ld.so)
    so this will add all of those paths.
 
@@ -49,9 +51,16 @@
   do							    		\
     {									\
       size_t len = strlen (dir);					\
-      char path[len + 9];						\
+      char path[len + 10];						\
       memcpy (path, dir, len + 1);					\
-      if (len >= 12 && ! memcmp(path + len - 12, "/lib64/lp64d", 12))	\
+      if (len >= 13 && ! memcmp(path + len - 13, "/lib32/ilp32d", 13))	\
+        {								\
+          len -= 9;							\
+	  path[len] = '\0';						\
+        }								\
+      if (len >= 12							\
+          && (! memcmp(path + len - 12, "/lib32/ilp32", 12)		\
+              || ! memcmp(path + len - 12, "/lib64/lp64d", 12)))	\
 	{								\
 	  len -= 8;							\
 	  path[len] = '\0';						\
@@ -64,6 +73,10 @@
       add_dir (path);							\
       if (len >= 4 && ! memcmp(path + len - 4, "/lib", 4))		\
 	{								\
+	  memcpy (path + len, "32/ilp32d", 10);				\
+	  add_dir (path);						\
+	  memcpy (path + len, "32/ilp32", 9);				\
+	  add_dir (path);						\
 	  memcpy (path + len, "64/lp64d", 9);				\
 	  add_dir (path);						\
 	  memcpy (path + len, "64/lp64", 8);				\