Skip building libtiff tools on all platforms

build_usd.py now patches the libtiff build to skip
building the included tools, most notably tiffgt,
on Linux and MacOS. This removes a GLUT
dependency that is otherwise unnecessary.

The build script had already been doing this on
Windows for other reasons; this change extends
this behavior to all other platforms.

Fixes #402

(Internal change: 1843826)

build_scripts/build_usd.py

@@ -545,26 +545,19 @@ def InstallJPEG_Lib(context, force):
 TIFF_URL = "ftp://download.osgeo.org/libtiff/tiff-4.0.7.zip"
 
 def InstallTIFF(context, force):
-    if Windows():
-        InstallTIFF_Windows(context, force)
-    else:
-        InstallTIFF_LinuxOrMacOS(context, force)
-
-def InstallTIFF_Windows(context, force):
     with CurrentWorkingDirectory(DownloadURL(TIFF_URL, context, force)):
         # libTIFF has a build issue on Windows where tools/tiffgt.c
         # unconditionally includes unistd.h, which does not exist.
         # To avoid this, we patch the CMakeLists.txt to skip building
-        # the tools entirely. We also need to skip building tests, since
-        # they rely on the tools we've just elided.
+        # the tools entirely. We do this on Linux and MacOS as well
+        # to avoid requiring some GL and X dependencies.
+        #
+        # We also need to skip building tests, since they rely on 
+        # the tools we've just elided.
         PatchFile("CMakeLists.txt", 
                    [("add_subdirectory(tools)", "# add_subdirectory(tools)"),
                     ("add_subdirectory(test)", "# add_subdirectory(test)")])
         RunCMake(context, force)
-
-def InstallTIFF_LinuxOrMacOS(context, force):
-    with CurrentWorkingDirectory(DownloadURL(TIFF_URL, context, force)):
-        RunCMake(context, force)
 
 TIFF = Dependency("TIFF", InstallTIFF, "include/tiff.h")