[UCRT] Use GCC inline assembler

Clang requires the asm to be split, otherwise it complains that it doesn't have enough registers.

sdk/include/ucrt/fenv.h

···
                     // next floating point instruction.  If we're using /arch:IA32,
                     // force the exception to be raised immediately:
                     #if defined _M_IX86 && _M_IX86_FP == 0 && !defined _M_HYBRID_X86_ARM64
+                    #ifdef _MSC_VER
                     __asm fwait;
+                    #else
+                    __asm__ __volatile__("fwait");
+                    #endif
                     #endif
                 }
             }

sdk/lib/ucrt/inc/corecrt_internal_big_integer.h

···
         uint32_t const multiplier
         ) throw()
     {
+       #ifdef _MSC_VER
         __asm
         {
             mov eax, dword ptr [multiplicand + 4]
···
 
             add edx, ecx
         }
+        #else // ^^^ _MSC_VER ^^^ // vvv !_MSC_VER vvv //
+	    uint64_t retval;
+	    __asm__(
+            "mull %[multiplier]\n"
+            "movl %%eax, %%ecx\n"
+            "movl %[multiplicand_lo], %%eax\n"
+            "mull %[multiplier]\n"
+            "addl %%ecx, %%edx\n"
+            : "=A" (retval)
+            : [multiplicand_hi] "a" ((uint32_t)((multiplicand >> 32) & 0xFFFFFFFF)),
+              [multiplicand_lo] "rm" ((uint32_t)((multiplicand >>  0) & 0xFFFFFFFF)),
+              [multiplier] "rm" (multiplier)
+            : "ecx" );
+        return retval;
+        #endif // !_MSC_VER
     }
 #else
     __forceinline uint64_t __cdecl multiply_64_32(
···
         }
 
         // Multiply and subtract.  Note that uu_quo may be one too large.  If
-        // we have a borrow at the end, we'll add the denominator back on and 
+        // we have a borrow at the end, we'll add the denominator back on and
         // decrement uu_quo.
         if (uu_quo > 0)
         {

sdk/lib/ucrt/misc/invalid_parameter.cpp

···
         EXCEPTION_POINTERS ExceptionPointers = {&ExceptionRecord, &ContextRecord};
 
         #ifdef _M_IX86
-
+        #if defined(__GNUC__) || defined(__clang__)
+        __asm__ __volatile__(
+            "movl %%eax, %[CxEax]\n\t"
+            "movl %%ecx, %[CxEcx]\n\t"
+            "movl %%edx, %[CxEdx]\n\t"
+            "movl %%ebx, %[CxEbx]\n\t"
+            "movl %%esi, %[CxEsi]\n\t"
+            "movl %%edi, %[CxEdi]\n\t"
+            : [CxEax] "=m" (ContextRecord.Eax),
+              [CxEcx] "=m" (ContextRecord.Ecx),
+              [CxEdx] "=m" (ContextRecord.Edx),
+              [CxEbx] "=m" (ContextRecord.Ebx),
+              [CxEsi] "=m" (ContextRecord.Esi),
+              [CxEdi] "=m" (ContextRecord.Edi));
+        __asm__ __volatile__(
+            "movw %%ss, %[CxSegSs]\n\t"
+            "movw %%cs, %[CxSegCs]\n\t"
+            "movw %%ds, %[CxSegDs]\n\t"
+            "movw %%es, %[CxSegEs]\n\t"
+            "movw %%fs, %[CxSegFs]\n\t"
+            "movw %%gs, %[CxSegGs]\n\t"
+            : [CxSegSs] "=m" (ContextRecord.SegSs),
+              [CxSegCs] "=m" (ContextRecord.SegCs),
+              [CxSegDs] "=m" (ContextRecord.SegDs),
+              [CxSegEs] "=m" (ContextRecord.SegEs),
+              [CxSegFs] "=m" (ContextRecord.SegFs),
+              [CxSegGs] "=m" (ContextRecord.SegGs));
+        __asm__ __volatile__(
+            "pushfl\n\t"
+            "popl %[CxEFlags]\n\t"
+            : [CxEFlags] "=m" (ContextRecord.EFlags));
+        #else // ^^^ __GNUC__ ^^^ // vvv !__GNUC__ vvv //
         __asm
         {
             mov dword ptr [ContextRecord.Eax  ], eax
···
             pushfd
             pop [ContextRecord.EFlags]
         }
+        #endif // !__GNUC__
 
         ContextRecord.ContextFlags = CONTEXT_CONTROL;