Add eabihf ABI support and set vendor-sys of bare-metal targets (#2745)

Set the vendor-sys of bare-metal targets to "-unknown-none-",
and currently only add "thumbxxx" to the bare-metal target list.

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

core/iwasm/compilation/aot_llvm.c

@@ -1915,6 +1915,7 @@ static ArchItem valid_archs[] = {
 static const char *valid_abis[] = {
     "gnu",
     "eabi",
+    "eabihf",
     "gnueabihf",
     "msvc",
     "ilp32",
@@ -1992,6 +1993,18 @@ get_target_arch_from_triple(const char *triple, char *arch_buf, uint32 buf_size)
     bh_assert(*triple == '-' || *triple == '\0');
 }
 
+static bool
+is_baremetal_target(const char *target, const char *cpu, const char *abi)
+{
+    /* TODO: support more baremetal targets */
+    if (target) {
+        /* If target is thumbxxx, then it is baremetal target */
+        if (!strncmp(target, "thumb", strlen("thumb")))
+            return true;
+    }
+    return false;
+}
+
 void
 aot_handle_llvm_errmsg(const char *string, LLVMErrorRef err)
 {
@@ -2214,7 +2227,7 @@ aot_create_comp_context(const AOTCompData *comp_data, aot_comp_option_t option)
     char *triple_norm_new = NULL, *cpu_new = NULL;
     char *err = NULL, *fp_round = "round.tonearest",
          *fp_exce = "fpexcept.strict";
-    char triple_buf[32] = { 0 }, features_buf[128] = { 0 };
+    char triple_buf[128] = { 0 }, features_buf[128] = { 0 };
     uint32 opt_level, size_level, i;
     LLVMCodeModel code_model;
     LLVMTargetDataRef target_data_ref;
@@ -2510,6 +2523,7 @@ aot_create_comp_context(const AOTCompData *comp_data, aot_comp_option_t option)
              * for Windows/MacOS under Linux host, or generating AOT file for
              * Linux/MacOS under Windows host.
              */
+
             if (!strcmp(abi, "msvc")) {
                 if (!strcmp(arch1, "i386"))
                     vendor_sys = "-pc-win32-";
@@ -2517,7 +2531,10 @@ aot_create_comp_context(const AOTCompData *comp_data, aot_comp_option_t option)
                     vendor_sys = "-pc-windows-";
             }
             else {
-                vendor_sys = "-pc-linux-";
+                if (is_baremetal_target(arch, cpu, abi))
+                    vendor_sys = "-unknown-none-";
+                else
+                    vendor_sys = "-pc-linux-";
             }
 
             bh_assert(strlen(arch1) + strlen(vendor_sys) + strlen(abi)
@@ -2553,6 +2570,9 @@ aot_create_comp_context(const AOTCompData *comp_data, aot_comp_option_t option)
                 if (!abi)
                     abi = "msvc";
             }
+            else if (is_baremetal_target(arch, cpu, abi)) {
+                vendor_sys = "-unknown-none-";
+            }
             else {
                 vendor_sys = "-pc-linux-";
                 if (!abi)