Add musl/OHOS compatibility: dlopen caching, _LARGEFILE64_SOURCE, config.guess

* configure.ac: Check for dlopen in libc before trying -ldl. On musl
  (and OpenHarmony), dlopen is part of libc with no separate libdl.

* configure.ac: Add _LARGEFILE64_SOURCE fallback detection for fopen64.
  On musl, fopen64 needs this define to be declared; glibc exposes it
  via _LARGEFILE_SOURCE alone.

* config.guess: Recognize HarmonyOS uname -s output and canonicalize
  as *-unknown-linux-ohos.

config.guess

@@ -940,6 +940,9 @@ EOF
     *:SerenityOS:*:*)
         GUESS=$UNAME_MACHINE-pc-serenity
         ;;
+    *:HarmonyOS:*:*)
+        GUESS=$UNAME_MACHINE-unknown-linux-ohos
+        ;;
     *:Interix*:*)
 	case $UNAME_MACHINE in
 	    x86)
@@ -952,7 +955,7 @@ EOF
 		GUESS=ia64-unknown-interix$UNAME_RELEASE
 		;;
 	esac ;;
-    i*:UWIN*:*)
+    i*:UWIN:*:*)
 	GUESS=$UNAME_MACHINE-pc-uwin
 	;;
     amd64:CYGWIN*:*:* | x86_64:CYGWIN*:*:*)

configure.ac

@@ -274,7 +274,9 @@ AC_MSG_RESULT($do_times)
 AC_CHECK_HEADERS(dlfcn.h dl.h, break)
 
 DLLIB=''
-AC_CHECK_LIB(dl,dlopen,[DLLIB=-ldl])
+# First check if dlopen is in libc (musl, OHOS, etc.)
+AC_CHECK_FUNC(dlopen, [DLLIB=],
+  [AC_CHECK_LIB(dl,dlopen,[DLLIB=-ldl])])
 if test -z "$DLLIB" ; then
 AC_CHECK_LIB(dld,shl_load,[DLLIB=-ldld])
 fi
@@ -363,6 +365,16 @@ AC_CHECK_FUNCS(realpath)
 # Check that these functions exist. They are mostly C99
 # functions that older compilers may not yet support.
 AC_CHECK_FUNCS(fopen64)
+# On musl-based systems, fopen64 may need _LARGEFILE64_SOURCE to be
+# declared. Try again with it defined if the first check failed.
+if test "$ac_cv_func_fopen64" != yes; then
+  iverilog_saved_cppflags="$CPPFLAGS"
+  CPPFLAGS="-D_LARGEFILE64_SOURCE $CPPFLAGS"
+  AC_CHECK_FUNCS(fopen64,
+    [AC_DEFINE([_LARGEFILE64_SOURCE], [1],
+      [Define to 1 if _LARGEFILE64_SOURCE is needed for fopen64])])
+  CPPFLAGS="$iverilog_saved_cppflags"
+fi
 # The following math functions may be defined in the math library so look
 # in the default libraries first and then look in -lm for them. On some
 # systems we may need to use the compiler in C99 mode to get a definition.