[MacPorts] #54773: port:libgcc/port:gcc7: proposed modifications, efficiency + libc++ support

[MacPorts]

#54773: port:libgcc/port:gcc7: proposed modifications, efficiency + libc++ support
--------------------------+----------------------
  Reporter:  RJVB         |      Owner:
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:  haspatch
      Port:  gcc7 libgcc  |
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Comment (by jeremyhu):

 > What I don't get is why it doesn't simply invoke clang.

 Because that's not what it's doing in as/driver.c.  We can have it do
 whatever we want.  I don't think searching $PATH for clang is good though
 because then we get nondeterministic behavior.  We should have it envoke a
 fully qualified path or fail.

 The purpose of port:libgcc is't about depending on specific compiler
 versions or not.  It's about making sure that all the gcc compilers use
 the same (newest) runtime libraries to avoid pulling multiple copies into
 a single process.

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Ticket URL: <https://trac.macports.org/ticket/54773#comment:8>
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