Give end-marker symbols their own addresses to fix a linker bug

It seems there is a linker bug related to control-flow guard that is
causing dotnet#66969. In eb8460f a thunktemplates.asm file was added that has
a LEAF_END_MARKED at the end of the file. This creates two symbols for
the same upcoming address. Normally that should be fine, but in this
case it causes the linker to place the same address twice in a CFG table
in the PE file. This causes the kernel to fail while loading the image.

A simple workaround would be to add a nop at the end of
thunktemplates.asm, but @janvorli suggested giving these symbols their
own address in all cases for goodness when debugging. We already do so
for Windows x64 it looks like.

Fix dotnet#66969

src/coreclr/pal/inc/unixasmmacrosamd64.inc

@@ -51,6 +51,8 @@ C_FUNC(\Name):
 .macro LEAF_END_MARKED Name, Section
 C_FUNC(\Name\()_End):
         .global C_FUNC(\Name\()_End)
+        ; make sure this symbol gets its own address
+        nop
         LEAF_END \Name, \Section
 .endm
 

src/coreclr/pal/inc/unixasmmacrosarm.inc

@@ -39,6 +39,8 @@ C_FUNC(\Name):
         .thumb_func
         .global C_FUNC(\Name\()_End)
 C_FUNC(\Name\()_End):
+        ; make sure this symbol gets its own address
+        nop
         LEAF_END \Name, \Section
 .endm
 

src/coreclr/pal/inc/unixasmmacrosarm64.inc

@@ -43,6 +43,8 @@ C_FUNC(\Name):
 .macro LEAF_END_MARKED Name, Section
 C_FUNC(\Name\()_End):
         .global C_FUNC(\Name\()_End)
+        ; make sure this symbol gets its own address
+        nop
         LEAF_END \Name, \Section
 .endm
 

src/coreclr/pal/inc/unixasmmacrosx86.inc

@@ -32,6 +32,8 @@ C_FUNC(\Name):
 .macro LEAF_END_MARKED Name, Section
 C_FUNC(\Name\()_End):
         .global C_FUNC(\Name\()_End)
+        ; make sure this symbol gets its own address
+        nop
         LEAF_END \Name, \Section
 .endm
 

src/coreclr/vm/arm/asmmacros.h

@@ -29,6 +29,9 @@ __EndLabelName SETS "$FuncName":CC:"_End"
 
     LEAF_END $FuncName
 
+    ; Make sure this symbol gets its own address
+    nop
+
     MEND
 
 ;-----------------------------------------------------------------------------

src/coreclr/vm/arm64/asmmacros.h

@@ -147,6 +147,9 @@ __EndLabelName SETS "$FuncName":CC:"_End"
 
     LEAF_END $FuncName
 
+    ; make sure this symbol gets its own address
+    nop
+
     MEND
 ;-----------------------------------------------------------------------------
 ; Macro use for enabling C++ to know where to patch code at runtime.

src/coreclr/vm/i386/AsmMacros.inc

@@ -37,6 +37,8 @@ LEAF_END_MARKED macro functionName
     endMarkerName TEXTEQU @CatStr(%bareFunctionName, <_End@0>)
     %endMarkerName:
     PUBLIC endMarkerName
+    ; make sure this symbol gets its own address
+    nop
     functionName ENDP
 endm