added --nimMainPrefix switch; fixes #15955; refs #16945 [backport:1.6] (#19235)

doc/advopt.txt

@@ -135,6 +135,8 @@ Advanced options:
   --cppCompileToNamespace:namespace
                             use the provided namespace for the generated C++ code,
                             if no namespace is provided "Nim" will be used
+  --nimMainPrefix:prefix    use `{prefix}NimMain` instead of `NimMain` in the produced
+                            C/C++ code
   --expandMacro:MACRO       dump every generated AST from MACRO
   --expandArc:PROCNAME      show how PROCNAME looks like after diverse optimizations
                             before the final backend phase (mostly ARC/ORC specific)

doc/backends.rst

@@ -246,6 +246,9 @@ Also, C code requires you to specify a forward declaration for functions or
 the compiler will assume certain types for the return value and parameters
 which will likely make your program crash at runtime.
 
+The name `NimMain` can be influenced via the `--nimMainPrefix:prefix` switch.
+Use `--nimMainPrefix:MyLib` and the function to call is named `MyLibNimMain`.
+
 
 Nim invocation example from C
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

doc/nimc.rst

@@ -385,6 +385,10 @@ of your program.
     NimMain() # initialize garbage collector memory, types and stack
 
 
+The name `NimMain` can be influenced via the `--nimMainPrefix:prefix` switch.
+Use `--nimMainPrefix:MyLib` and the function to call is named `MyLibNimMain`.
+
+
 Cross-compilation for iOS
 =========================
 
@@ -413,6 +417,9 @@ of your program.
 Note: XCode's "make clean" gets confused about the generated nim.c files,
 so you need to clean those files manually to do a clean build.
 
+The name `NimMain` can be influenced via the `--nimMainPrefix:prefix` switch.
+Use `--nimMainPrefix:MyLib` and the function to call is named `MyLibNimMain`.
+
 
 Cross-compilation for Nintendo Switch
 =====================================