Update literals regression test to execute (even if it doesn't execute anything)

Author: hsutter

regression-tests/mixed-float-literals.cpp2

@@ -54,7 +54,7 @@ void literals_cpp1() {
   // 1e - 10.0f;
 }
 
-literals_cpp2: () -> auto = {
+literals_cpp2: () = {
   // integers
   123;
   123u;
@@ -108,4 +108,6 @@ literals_cpp2: () -> auto = {
   // 1e - 10.0;
   // 1e - 10f;
   // 1e - 10.0f;
-}
+}
+
+main: ()->int = { }

regression-tests/test-results/clang-12/mixed-float-literals.cpp.execution

@@ -239,6 +239,3 @@ mixed-float-literals.cpp2:99:3: warning: expression result unused [-Wunused-valu
   1E-1'0;
   ^~~~~~
 80 warnings generated.
-/usr/bin/ld: /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crt1.o: in function `_start':
-(.text+0x24): undefined reference to `main'
-clang: error: linker command failed with exit code 1 (use -v to see invocation)

regression-tests/test-results/clang-12/mixed-float-literals.cpp.output

@@ -1,3 +0,0 @@
-/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/Scrt1.o: in function `_start':
-(.text+0x24): undefined reference to `main'
-collect2: error: ld returned 1 exit status

regression-tests/test-results/gcc-10/mixed-float-literals.cpp.execution

@@ -58,13 +58,15 @@ void literals_cpp1() {
   // 1e - 10.0f;
 }
 
-[[nodiscard]] auto literals_cpp2() -> auto;
+auto literals_cpp2() -> void;
+#line 113 "mixed-float-literals.cpp2"
+[[nodiscard]] auto main() -> int;
 
 //=== Cpp2 definitions ==========================================================
 
 #line 56 "mixed-float-literals.cpp2"
 
-[[nodiscard]] auto literals_cpp2() -> auto{
+auto literals_cpp2() -> void{
   // integers
   123;
   123u;
@@ -120,3 +122,5 @@ void literals_cpp1() {
   // 1e - 10.0f;
 }
 
+[[nodiscard]] auto main() -> int{}
+

regression-tests/test-results/gcc-10/mixed-float-literals.cpp.output

@@ -1,2 +1 @@
 mixed-float-literals.cpp
-LINK : fatal error LNK1561: entry point must be defined