Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Set this via cflags
  CDRIVER-1104 Don't error when adding -pthread on clang

Author: ajdavis

.evergreen/compile-unix.sh

@@ -61,7 +61,7 @@ install_openssl () {
    cd ..
 
    # x505_vfy.h has issues in 1.1.0e
-   export CPPFLAGS=-Wno-redundant-decls
+   export CFLAGS=-Wno-redundant-decls
    export PKG_CONFIG_PATH=$INSTALL_DIR/lib/pkgconfig
    export EXTRA_LIB_PATH="$INSTALL_DIR/lib"
    SSL="openssl";

build/autotools/PlatformFlags.m4

@@ -6,6 +6,8 @@ AS_IF([test "$os_darwin" = "yes"],
       [AX_CHECK_COMPILE_FLAG([-Wno-cast-align], [CFLAGS="$CFLAGS -Wno-cast-align"])])
 AS_IF([test "$os_darwin" = "yes"],
       [AX_CHECK_COMPILE_FLAG([-Wno-unneeded-internal-declaration], [CFLAGS="$CFLAGS -Wno-unneeded-internal-declaration"])])
+AS_IF([test "$os_darwin" = "yes"],
+      [AX_CHECK_COMPILE_FLAG([-Wno-error=unused-command-line-argument], [CFLAGS="$CFLAGS -Wno-error=unused-command-line-argument"])])
 dnl We know there are some cast-align issues on Solaris
 AS_IF([test "$os_solaris" = "yes"],
       [AX_CHECK_COMPILE_FLAG([-Wno-cast-align], [CFLAGS="$CFLAGS -Wno-cast-align"])])