[OBJ2BIN] Use section flags instead of a hardcoded ".text" name (#5317)

A 32-bit ASM file can turn into an empty binary file in certain cases (compiled with MSVC).
MASM/ML produces a ".text$mn" section instead of the ".text", which makes obj2bin generate an empty binary file.

The problem didn't occur with our 16-bit artifacts (16-bit stubs, bootsectors...), because their object files all have similar sections pattern: the ".text" section and empty ".text$mn" section, which didn't matter since it is empty.
On the contrary, the .text$mn section(s) aren't empty for 32-bit stubs.

sdk/tools/obj2bin/obj2bin.c

@@ -140,8 +140,9 @@ int main(int argc, char *argv[])
     /* Loop all sections */
     for (i = 0; i < pFileHeader->NumberOfSections; i++)
     {
-        /* Check if this is '.text' section */
-        if ((strcmp((char*)pSectionHeader->Name, ".text") == 0) &&
+        /* Check if this is a section with executable code */
+        if (((pSectionHeader->Characteristics & (IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE)) ==
+             (IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE)) &&
             (pSectionHeader->SizeOfRawData != 0))
         {
             if (!RelocateSection(pData,