Homebrew patch to show output of build commands (or other subprocs), and to *not* set `-DCMAKE_VERBOSE_MAKEFILE` unless `-v` is passed

homebrew_keep_output.patch

diff --git a/Library/Homebrew/env_config.rb b/Library/Homebrew/env_config.rb
index 03bb33852..5eadae8ff 100644
--- a/Library/Homebrew/env_config.rb
+++ b/Library/Homebrew/env_config.rb
@@ -399,6 +399,10 @@ module Homebrew
       SUDO_ASKPASS:                              {
         description: "If set, pass the `-A` option when calling `sudo`(8).",
       },
+      HOMEBREW_KEEP_OUTPUT:                      {
+        description: "If set, system commands run by Homebrew will not have their output suppressed.",
+        boolean:     true,
+      },
       all_proxy:                                 {
         description: "Use this SOCKS5 proxy for `curl`(1), `git`(1) and `svn`(1) when downloading through Homebrew.",
       },
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 44240c9d9..e6118e678 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1653,11 +1653,12 @@ class Formula
       -DCMAKE_INSTALL_LIBDIR=#{install_libdir}
       -DCMAKE_BUILD_TYPE=Release
       -DCMAKE_FIND_FRAMEWORK=#{find_framework}
-      -DCMAKE_VERBOSE_MAKEFILE=ON
       -Wno-dev
       -DBUILD_TESTING=OFF
     ]
 
+    args << "-DCMAKE_VERBOSE_MAKEFILE=ON" if verbose?
+
     # Avoid false positives for clock_gettime support on 10.11.
     # CMake cache entries for other weak symbols may be added here as needed.
     args << "-DHAVE_CLOCK_GETTIME:INTERNAL=0" if MacOS.version == "10.11" && MacOS::Xcode.version >= "8.0"
@@ -2678,7 +2679,7 @@ class Formula
       log.puts Time.now, "", cmd, args, ""
       log.flush
 
-      if verbose?
+      if verbose? || Homebrew::EnvConfig.keep_output?
         rd, wr = IO.pipe
         begin
           pid = fork do