9996 use GCC 7 as default primary compiler

*** 26,36 ****
  # Copyright 2015, OmniTI Computer Consulting, Inc. All rights reserved.
  # Copyright 2015 Gary Mills
  # Copyright 2015 Igor Kozhukhov <ikozhukhov@gmail.com>
  # Copyright 2016 Toomas Soome <tsoome@me.com>
  # Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
! # Copyright (c) 2019, Joyent, Inc.
  #
  
  #
  # Makefile.master, global definitions for system source
  #
--- 26,36 ----
  # Copyright 2015, OmniTI Computer Consulting, Inc. All rights reserved.
  # Copyright 2015 Gary Mills
  # Copyright 2015 Igor Kozhukhov <ikozhukhov@gmail.com>
  # Copyright 2016 Toomas Soome <tsoome@me.com>
  # Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
! # Copyright 2019, Joyent, Inc.
  #
  
  #
  # Makefile.master, global definitions for system source
  #
*** 124,134 ****
  # Build uses java7 by default.  Pass one the variables below set to empty
  # string in the environment to override.
  BLD_JAVA_6=     $(POUND_SIGN)
  BLD_JAVA_8=     $(POUND_SIGN)
  
! GNUC_ROOT=      /opt/gcc/4.4.4
  GCCLIBDIR=      $(GNUC_ROOT)/lib
  GCCLIBDIR64=    $(GNUC_ROOT)/lib/$(MACH64)
  
  DOCBOOK_XSL_ROOT=       /usr/share/sgml/docbook/xsl-stylesheets
  
--- 124,134 ----
  # Build uses java7 by default.  Pass one the variables below set to empty
  # string in the environment to override.
  BLD_JAVA_6=     $(POUND_SIGN)
  BLD_JAVA_8=     $(POUND_SIGN)
  
! GNUC_ROOT=      /usr/gcc/7
  GCCLIBDIR=      $(GNUC_ROOT)/lib
  GCCLIBDIR64=    $(GNUC_ROOT)/lib/$(MACH64)
  
  DOCBOOK_XSL_ROOT=       /usr/share/sgml/docbook/xsl-stylesheets
  
*** 840,852 ****
  #
  SPRO_ROOT=              $(BUILD_TOOLS)/SUNWspro
  SPRO_VROOT=             $(SPRO_ROOT)/SS12
  GNU_ROOT=               /usr
  
! $(__GNUC)PRIMARY_CC=    gcc4,$(GNUC_ROOT)/bin/gcc,gnu
  $(__SUNC)PRIMARY_CC=    studio12,$(SPRO_VROOT)/bin/cc,sun
! $(__GNUC)PRIMARY_CCC=   gcc4,$(GNUC_ROOT)/bin/g++,gnu
  $(__SUNC)PRIMARY_CCC=   studio12,$(SPRO_VROOT)/bin/CC,sun
  
  CW_CC_COMPILERS=        $(PRIMARY_CC:%=--primary %) $(SHADOW_CCS:%=--shadow %)
  CW_CCC_COMPILERS=       $(PRIMARY_CCC:%=--primary %) $(SHADOW_CCCS:%=--shadow %)
  
--- 840,852 ----
  #
  SPRO_ROOT=              $(BUILD_TOOLS)/SUNWspro
  SPRO_VROOT=             $(SPRO_ROOT)/SS12
  GNU_ROOT=               /usr
  
! $(__GNUC)PRIMARY_CC=    gcc7,$(GNUC_ROOT)/bin/gcc,gnu
  $(__SUNC)PRIMARY_CC=    studio12,$(SPRO_VROOT)/bin/cc,sun
! $(__GNUC)PRIMARY_CCC=   gcc7,$(GNUC_ROOT)/bin/g++,gnu
  $(__SUNC)PRIMARY_CCC=   studio12,$(SPRO_VROOT)/bin/CC,sun
  
  CW_CC_COMPILERS=        $(PRIMARY_CC:%=--primary %) $(SHADOW_CCS:%=--shadow %)
  CW_CCC_COMPILERS=       $(PRIMARY_CCC:%=--primary %) $(SHADOW_CCCS:%=--shadow %)