[x86/Linux] Fix undefined references in libmscordbi.so on x86

Asm block like following:
__asm fnsave currentFPUState

where currentFPUState is structure works with MSVC but leads to
undefined reference currentFPUState in the binary with other
compilers. So rewrite such asm blocks for them.

This patch fixes error "Unable to load 'libmscordbi.so'" during
execution of 'clrstack -f' command of SOS plugin on x86.

src/debug/di/rsthread.cpp

@@ -1471,7 +1471,15 @@ void CordbThread::Get32bitFPRegisters(CONTEXT * pContext)
 
     FLOATING_SAVE_AREA currentFPUState;
 
+#ifdef _MSC_VER
     __asm fnsave currentFPUState // save the current FPU state.
+#else
+    __asm__ __volatile__
+    (
+        "  fnsave %0\n" \
+        : "=m"(currentFPUState)
+    );
+#endif
 
     floatarea.StatusWord &= 0xFF00; // remove any error codes.
     floatarea.ControlWord |= 0x3F; // mask all exceptions.
@@ -1482,12 +1490,22 @@ void CordbThread::Get32bitFPRegisters(CONTEXT * pContext)
     // @dbgtodo Microsoft crossplat: the conversion from a series of bytes to a floating 
     // point value will need to be done with an explicit conversion routine to unpack
     // the IEEE format and compute the real number value represented. 
-
+
+#ifdef _MSC_VER
     __asm
     {
         fninit
         frstor floatarea          ;; reload the threads FPU state.
     }
+#else
+    __asm__
+    (
+        "  fninit\n" \
+        "  frstor %0\n" \
+        : /* no outputs */
+        : "m"(floatarea)
+    );
+#endif
 
     unsigned int i;
 
@@ -1498,11 +1516,21 @@ void CordbThread::Get32bitFPRegisters(CONTEXT * pContext)
         m_floatValues[i] = td;
     }
 
+#ifdef _MSC_VER
     __asm
     {
         fninit
         frstor currentFPUState    ;; restore our saved FPU state.
     }
+#else
+    __asm__
+    (
+        "  fninit\n" \
+        "  frstor %0\n" \
+        : /* no outputs */
+        : "m"(currentFPUState)
+    );
+#endif
 
     m_fFloatStateValid = true;
     m_floatStackTop = floatStackTop;

src/debug/di/valuehome.cpp

@@ -481,18 +481,36 @@ void FloatRegValueHome::SetEnregisteredValue(MemoryRange newValue,
     // restore our original state.
     DT_FLOATING_SAVE_AREA currentFPUState;
 
+    #ifdef _MSC_VER
     __asm fnsave currentFPUState // save the current FPU state.
+    #else
+    __asm__ __volatile__
+    (
+        "  fnsave %0\n" \
+        : "=m"(currentFPUState)
+    );
+    #endif
 
     // Copy the state out of the context.
     DT_FLOATING_SAVE_AREA floatarea = pContext->FloatSave;
     floatarea.StatusWord &= 0xFF00; // remove any error codes.
     floatarea.ControlWord |= 0x3F; // mask all exceptions.
 
+    #ifdef _MSC_VER
     __asm
     {
         fninit
         frstor floatarea          ;; reload the threads FPU state.
     }
+    #else
+    __asm__
+    (
+        "  fninit\n" \
+        "  frstor %0\n" \
+        : /* no outputs */
+        : "m"(floatarea)
+    );
+    #endif
 
     double td; // temp double
     double popArea[DebuggerIPCE_FloatCount];
@@ -519,17 +537,35 @@ void FloatRegValueHome::SetEnregisteredValue(MemoryRange newValue,
     }
 
     // Save out the modified float area.
+    #ifdef _MSC_VER
     __asm fnsave floatarea
+    #else
+    __asm__ __volatile__
+    (
+        "  fnsave %0\n" \
+        : "=m"(floatarea)
+    );
+    #endif
 
     // Put it into the context.
     pContext->FloatSave= floatarea;
 
     // Restore our FPU state
+    #ifdef _MSC_VER
     __asm
     {
         fninit
         frstor currentFPUState    ;; restore our saved FPU state.
     }
+    #else
+    __asm__
+    (
+        "  fninit\n" \
+        "  frstor %0\n" \
+        : /* no outputs */
+        : "m"(currentFPUState)
+    );
+    #endif
     #endif // DBG_TARGET_X86
 
     // update the thread's floating point stack