libgloss: epiphany: rename symbol prefix cache var

Autoconf emits a warning for this:
configure.ac:75: warning: AC_CACHE_VAL(libc_symbol_prefix, ...): suspicious cache-id, must contain _cv_ to be cached

Rename the variable to match the naming in libnosys/ subdir.

libgloss/epiphany/configure

@@ -2030,13 +2030,13 @@ $as_echo "#define HAVE_ASM_POPSECTION_DIRECTIVE 1" >>confdefs.h
 # script work it out.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for symbol prefix" >&5
 $as_echo_n "checking for symbol prefix... " >&6; }
-if ${libc_symbol_prefix+:} false; then :
+if ${libc_cv_symbol_prefix+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   cat > conftest.c <<\EOF
 foo () { }
 EOF
-libc_symbol_prefix=none
+libc_cv_symbol_prefix=none
 if { ac_try='${CC-cc} -S conftest.c -o - | fgrep "\$foo" > /dev/null'
   { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
   (eval $ac_try) 2>&5
@@ -2044,7 +2044,7 @@ if { ac_try='${CC-cc} -S conftest.c -o - | fgrep "\$foo" > /dev/null'
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; };
 then
-  libc_symbol_prefix='$'
+  libc_cv_symbol_prefix='$'
 else
   if { ac_try='${CC-cc} -S conftest.c -o - | fgrep "_foo" > /dev/null'
   { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
@@ -2053,17 +2053,17 @@ else
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; };
   then
-    libc_symbol_prefix=_
+    libc_cv_symbol_prefix=_
   fi
 fi
 rm -f conftest*
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_symbol_prefix" >&5
-$as_echo "$libc_symbol_prefix" >&6; }
-if test $libc_symbol_prefix != none; then
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_symbol_prefix" >&5
+$as_echo "$libc_cv_symbol_prefix" >&6; }
+if test $libc_cv_symbol_prefix != none; then
 
 cat >>confdefs.h <<_ACEOF
-#define __SYMBOL_PREFIX "$libc_symbol_prefix"
+#define __SYMBOL_PREFIX "$libc_cv_symbol_prefix"
 _ACEOF
 
 else

libgloss/epiphany/configure.ac

@@ -72,24 +72,24 @@ AC_DEFINE(HAVE_ASM_POPSECTION_DIRECTIVE, 1,
 
 # Sort out what the symbol prefix is (we could just fix it as '_', but let the
 # script work it out.
-AC_CACHE_CHECK([for symbol prefix], libc_symbol_prefix, [dnl
+AC_CACHE_CHECK([for symbol prefix], libc_cv_symbol_prefix, [dnl
 cat > conftest.c <<\EOF
 foo () { }
 EOF
 dnl
-libc_symbol_prefix=none
+libc_cv_symbol_prefix=none
 if AC_TRY_COMMAND([${CC-cc} -S conftest.c -o - | fgrep "\$foo" > /dev/null]);
 then
-  libc_symbol_prefix='$'
+  libc_cv_symbol_prefix='$'
 else
   if AC_TRY_COMMAND([${CC-cc} -S conftest.c -o - | fgrep "_foo" > /dev/null]);
   then
-    libc_symbol_prefix=_
+    libc_cv_symbol_prefix=_
   fi
 fi
 rm -f conftest* ])
-if test $libc_symbol_prefix != none; then
-  AC_DEFINE_UNQUOTED(__SYMBOL_PREFIX, "$libc_symbol_prefix", [symbol prefix])
+if test $libc_cv_symbol_prefix != none; then
+  AC_DEFINE_UNQUOTED(__SYMBOL_PREFIX, "$libc_cv_symbol_prefix", [symbol prefix])
 else
   AC_DEFINE(__SYMBOL_PREFIX, "", [symbol prefix])
 fi