remove fails_with :gcc

fixes: #10

Author: tmcdonell

Formula/llvm-3.7.rb

@@ -95,9 +95,7 @@ def ver
   # LLVM installs its own standard library which confuses stdlib checking.
   cxxstdlib_check :skip
 
-  # Apple's libstdc++ is too old to build LLVM
-  fails_with :gcc
-
+  # http://releases.llvm.org/3.7.1/docs/CMake.html
   def install
     # One of llvm makefiles relies on gnu sed behavior to generate CMake modules correctly
     ENV.prepend_path "PATH", "#{Formula["gnu-sed"].opt_libexec}/gnubin"

Formula/llvm-3.8.rb

@@ -95,9 +95,7 @@ def ver
   # LLVM installs its own standard library which confuses stdlib checking.
   cxxstdlib_check :skip
 
-  # Apple's libstdc++ is too old to build LLVM
-  fails_with :gcc
-
+  # http://releases.llvm.org/3.8.1/docs/CMake.html
   def install
     # One of llvm makefiles relies on gnu sed behavior to generate CMake modules correctly
     ENV.prepend_path "PATH", "#{Formula["gnu-sed"].opt_libexec}/gnubin"

Formula/llvm-3.9.rb

@@ -90,11 +90,6 @@ class Llvm39 < Formula
   depends_on "libffi"
   depends_on "cmake" => :build
 
-  # requires gcc >= 4.7
-  ("4.3".."4.6").each do |n|
-    fails_with :gcc => n
-  end
-
   # version suffix
   def ver
     "3.9"

Formula/llvm-4.0.rb

@@ -90,11 +90,6 @@ class Llvm40 < Formula
   depends_on "libffi"
   depends_on "cmake" => :build
 
-  # requires gcc >= 4.8
-  ("4.3".."4.7").each do |n|
-    fails_with :gcc => n
-  end
-
   # version suffix
   def ver
     "4.0"

Formula/llvm-5.0.rb

@@ -92,11 +92,6 @@ class Llvm50 < Formula
   depends_on "libffi"
   depends_on "cmake" => :build
 
-  # requires gcc >= 4.8
-  ("4.3".."4.7").each do |n|
-    fails_with :gcc => n
-  end
-
   # version suffix
   def ver
     "5.0"

Formula/llvm-6.0.rb

@@ -92,11 +92,6 @@ class Llvm60 < Formula
   depends_on "libffi"
   depends_on "cmake" => :build
 
-  # requires gcc >= 4.8
-  ("4.3".."4.7").each do |n|
-    fails_with :gcc => n
-  end
-
   # version suffix
   def ver
     "6.0"

Formula/llvm-7.0.rb

@@ -92,11 +92,6 @@ class Llvm70 < Formula
   depends_on "libffi"
   depends_on "cmake" => :build
 
-  # requires gcc >= 4.8
-  ("4.3".."4.7").each do |n|
-    fails_with :gcc => n
-  end
-
   # version suffix
   def ver
     "7.0"