Update macOS build instructions (#950)

Author: adamweiss

getting-started/setup-building.rst

@@ -386,16 +386,22 @@ with **Homebrew**::
 
 For Python 3.10 and newer::
 
-    $ PKG_CONFIG_PATH="$(brew --prefix tcl-tk)/lib/pkgconfig" \
-      ./configure --with-pydebug --with-openssl=$(brew --prefix [email protected])
+    $ CFLAGS="-I$(brew --prefix gdbm)/include -I$(brew --prefix xz)/include" \
+      LDFLAGS="-L$(brew --prefix gdbm)/lib -I$(brew --prefix xz)/lib" \
+      PKG_CONFIG_PATH="$(brew --prefix tcl-tk)/lib/pkgconfig" \
+      ./configure --with-pydebug \
+                  --with-openssl=$(brew --prefix openssl)
+
 
 For Python versions 3.9 through 3.7::
 
-    $ export PKG_CONFIG_PATH="$(brew --prefix tcl-tk)/lib/pkgconfig"
-    $ ./configure --with-pydebug \
-                  --with-openssl=$(brew --prefix [email protected]) \
-                  --with-tcltk-libs="$(pkg-config --libs tcl tk)" \
-                  --with-tcltk-includes="$(pkg-config --cflags tcl tk)"
+    $ CFLAGS="-I$(brew --prefix gdbm)/include -I$(brew --prefix xz)/include" \
+      LDFLAGS="-L$(brew --prefix gdbm)/lib -L$(brew --prefix xz)/lib" \
+      PKG_CONFIG_PATH="$(brew --prefix tcl-tk)/lib/pkgconfig" \
+      ./configure --with-pydebug \
+              --with-openssl=$(brew --prefix [email protected]) \
+              --with-tcltk-libs="$(pkg-config --libs tcl tk)" \
+              --with-tcltk-includes="$(pkg-config --cflags tcl tk)"
 
 and ``make``::