diff --git a/buildbot/osuosl/master/config/builders.py b/buildbot/osuosl/master/config/builders.py
--- a/buildbot/osuosl/master/config/builders.py
+++ b/buildbot/osuosl/master/config/builders.py
@@ -183,6 +183,7 @@
                         "-DLLVM_TARGETS_TO_BUILD=ARM",
                         "-DTARGET_TRIPLE=armv7-unknown-linux-gnueabihf",
                         "-DDEFAULT_SYSROOT=C:/buildbot/.arm-ubuntu",
+                        "-DZLIB_ROOT=C:/buildbot/.zlib-win32",
                         "-DLLVM_LIT_ARGS=-v -vv --threads=32",
                         WithProperties("%(remote_test_host:+-DREMOTE_TEST_HOST=)s%(remote_test_host:-)s"),
                         WithProperties("%(remote_test_user:+-DREMOTE_TEST_USER=)s%(remote_test_user:-)s"),
@@ -221,6 +222,7 @@
                         "-DLLVM_TARGETS_TO_BUILD=AArch64",
                         "-DTARGET_TRIPLE=aarch64-unknown-linux-gnu",
                         "-DDEFAULT_SYSROOT=C:/buildbot/.aarch64-ubuntu",
+                        "-DZLIB_ROOT=C:/buildbot/.zlib-win32",
                         "-DLLVM_LIT_ARGS=-v -vv --threads=32",
                         WithProperties("%(remote_test_host:+-DREMOTE_TEST_HOST=)s%(remote_test_host:-)s"),
                         WithProperties("%(remote_test_user:+-DREMOTE_TEST_USER=)s%(remote_test_user:-)s"),
diff --git a/buildbot/osuosl/master/config/release_builders.py b/buildbot/osuosl/master/config/release_builders.py
--- a/buildbot/osuosl/master/config/release_builders.py
+++ b/buildbot/osuosl/master/config/release_builders.py
@@ -128,6 +128,7 @@
                         "-DLLVM_TARGETS_TO_BUILD=ARM",
                         "-DTARGET_TRIPLE=armv7-unknown-linux-gnueabihf",
                         "-DDEFAULT_SYSROOT=C:/buildbot/.arm-ubuntu",
+                        "-DZLIB_ROOT=C:/buildbot/.zlib-win32",
                         "-DLLVM_LIT_ARGS=-v -vv --threads=32",
                         WithProperties("%(remote_test_host:+-DREMOTE_TEST_HOST=)s%(remote_test_host:-)s"),
                         WithProperties("%(remote_test_user:+-DREMOTE_TEST_USER=)s%(remote_test_user:-)s"),
@@ -166,6 +167,7 @@
                         "-DLLVM_TARGETS_TO_BUILD=AArch64",
                         "-DTARGET_TRIPLE=aarch64-unknown-linux-gnu",
                         "-DDEFAULT_SYSROOT=C:/buildbot/.aarch64-ubuntu",
+                        "-DZLIB_ROOT=C:/buildbot/.zlib-win32",
                         "-DLLVM_LIT_ARGS=-v -vv --threads=32",
                         WithProperties("%(remote_test_host:+-DREMOTE_TEST_HOST=)s%(remote_test_host:-)s"),
                         WithProperties("%(remote_test_user:+-DREMOTE_TEST_USER=)s%(remote_test_user:-)s"),