GCC Dependencies

[Marcus Calhoun-Lopez]

Currently, the GCC dependencies on the various parts of libgcc seem somewhat inconsistent or at least difficult to follow.
Before I go to the trouble of creating a pull request, I thought someone might have some insights.
Here is what I propose:

gcc43, gcc44, gcc45:
    Library Dependencies: 
    Runtime Dependencies: libgcc45, libgcc6, libgcc7, libgcc

gcc46, gcc47, gcc48, gcc49, gcc5, gcc6:
    Library Dependencies: 
    Runtime Dependencies: libgcc6, libgcc7, libgcc

gcc7:
    Library Dependencies: 
    Runtime Dependencies: libgcc7, libgcc

gcc8:
    Library Dependencies: 
    Runtime Dependencies: libgcc

gcc9:
    Library Dependencies: 
    Runtime Dependencies: libgcc-devel

--------------------------------------------------

libgcc45:
    Library Dependencies:
    Runtime Dependencies:

libgcc6:
    Library Dependencies:
    Runtime Dependencies:

libgcc7:
    Library Dependencies: 
    Runtime Dependencies:


==============================================
This is the current status of things:
==============================================

gcc43, gcc44, gcc45:
    Library Dependencies: libgcc
    Runtime Dependencies: libgcc45 libgcc6

gcc46, gcc47, gcc48, gcc49, gcc5:
    Library Dependencies: libgcc
    Runtime Dependencies: libgcc6

gcc6:
    Library Dependencies: libgcc libgcc7
    Runtime Dependencies: libgcc6

gcc7:
    Library Dependencies: libgcc
    Runtime Dependencies: libgcc7

gcc8:
    Library Dependencies: libgcc
    Runtime Dependencies: 

gcc9:
    Library Dependencies: libgcc-devel
    Runtime Dependencies: 

--------------------------------------------------

libgcc45:
    Library Dependencies:
    Runtime Dependencies: 

libgcc6:
    Library Dependencies: llibgcc libgcc7
    Runtime Dependencies: 

libgcc7:
    Library Dependencies: llibgcc
    Runtime Dependencies: 

--------------------------------------------------

Port libgcc45 contains:
  /opt/local/lib/libgcc/libobjc-gnu.2.dylib


Port libgcc6 contains:
  /opt/local/lib/libgcc/libasan.3.dylib
  /opt/local/lib/libgcc/libgfortran.3.dylib


Port libgcc7 (for ${os.major}>=10) contains:
  /opt/local/lib/libgcc/libasan.4.dylib
  /opt/local/lib/libgcc/libcilkrts.5.dylib
  /opt/local/lib/libgcc/libgfortran.4.dylib
  /opt/local/lib/libgcc/libubsan.0.dylib


libgcc and libgcc-devel conflict
libgcc depends on
    libgcc8 if ${os.major}>=10
    libgcc7 otherwise