Build: Static on OSX, dynamic on Linux (esy-packages#14)

* Split out linux/OSX libraries; keep harfbuzz shared on linux

* Bring back dynamic linking for Linux

esy/configure-linux.sh

@@ -0,0 +1,2 @@
+cd _build
+./configure --prefix=$cur__install

package.json

@@ -7,7 +7,9 @@
   "esy": {
     "build": [
         ["./esy/prep.sh"],
-        ["bash", "-c", "#{os == 'windows' ? './esy/configure-windows.sh' : './esy/configure.sh'}"],
+        ["bash", "-c", "#{os == 'windows' ? './esy/configure-windows.sh' : 'echo'}"],
+        ["bash", "-c", "#{os == 'darwin' ? './esy/configure-osx.sh' : 'echo'}"],
+        ["bash", "-c", "#{os == 'linux' ? './esy/configure-linux.sh' : 'echo'}"],
         ["./esy/build.sh"]
     ],
     "buildsInSource": "_build",