Try to improve the wording a bit

Author: mjklemm

flang/docs/FlangDriver.md

@@ -172,7 +172,18 @@ translation units supplied as object files.
 By default, the Flang linker driver adds several libraries to the linker
 invocation to make sure that all entrypoints for program start
 (Fortran's program unit) and runtime routines can be resolved by the linker.
-The libraries are:
+
+An abridged example (only showing the Fortran specific linker flags, omission
+indicated by `[...]`) for such a linker invocation on a Linux system would look
+like this:
+
+```
+$ flang -v -o example example.o
+"/usr/bin/ld" [...] example.o [...] "--whole-archive" "-lFortran_main"
+"--no-whole-archive" "-lFortranRuntime" "-lFortranDecimal" [...]
+```
+
+The automatically added libraries are:
 
 * `Fortran_main`: Provides the main entry point `main` that then invokes
   `_QQmain` with the Fortran program unit.  This library has a dependency to
@@ -182,20 +193,25 @@ The libraries are:
 
 The default is that, when using Flang as the linker, one of the Fortran
 translation units provides the program unit and therefore it is assumed that
-Fortran is the main code part (calling into C/C++ routines via `BIND
-(C)` interfaces).  When composing the linker commandline, Flang uses
+Fortran is the main code part (calling into C/C++ routines via `BIND (C)`
+interfaces).  When composing the linker commandline, Flang uses
 `--whole-archive` and `--no-whole-archive` (Windows: `/WHOLEARCHIVE:`,
-Darwin: *not implemented yet*) to make sure that all for `Fortran_main` is
-processed by the linker.  This is done to issue a proper error message when
+Darwin & AIX: *not implemented yet*) to make sure that all for `Fortran_main`
+is processed by the linker.  This is done to issue a proper error message when
 multiple definitions of `main` occur.  This happens, for instance, when linking
 a code that has a Fortran program unit with a C/C++ code that also defines a
-`main` function.
-
-If the code is C/C++ based and invokes Fortran routines, either use Clang as the
-linker driver (supplying `FortranRuntime` and/or `FortranDecimal` to the linker
-driver) or use Flang with the `-fno-fortran-main` flag.  This flag removes
+`main` function.  A user may be required to explicitly provide the C++ runtime
+libraries at link time (e.g., via `-lstdc++` for STL)
+
+If the code is C/C++ based and invokes Fortran routines, one can either use Clang
+for Flang as the linker driver.  If Clang is used, it will automatically all
+required runtime libraries needed by C++ (e.g., for STL) to the linker invocation.
+In this case, one has to explicitly provide the Fortran runtime libraries
+`FortranRuntime` and/or `FortranDecimal`.  An alternative is to use Flang to link
+and use the `-fno-fortran-main` flag.  This flag removes
 `Fortran_main` from the linker stage and hence requires one of the C/C++
-translation units to provide a definition of the `main` function.
+translation units to provide a definition of the `main` function. In this case,
+it may be required to explicitly supply C++ runtime libraries as mentioned above.
 
 When creating shared or static libraries, `Fortran_main` is automatically
 removed from the linker stage.  It is assumed that when creating a static or