Don't clober the environment `CPPFLAGS` and `LDFLAGS` (refs #168)

Because the variables specified via command-line arguments for the
`./configure` will be favored than one in environment variables,
setting those variables in `PACKAGE_CONFIGURE_OPTS_ARRAY` will hide
existing environment variables.

To avoid the problem, stop using `package_option()` to setup those
variables.

plugins/python-build/bin/python-build

@@ -1047,7 +1047,8 @@ needs_yaml() {
 use_homebrew_yaml() {
   local libdir="$(brew --prefix libyaml 2>/dev/null || true)"
   if [ -d "$libdir" ]; then
-    package_option python configure CPPFLAGS="-I$libdir/include" LDFLAGS="-L$libdir/lib"
+    export CPPFLAGS="-I$libdir/include ${CPPFLAGS}"
+    export LDFLAGS="-L$libdir/lib ${LDFLAGS}"
   else
     return 1
   fi
@@ -1079,7 +1080,8 @@ use_homebrew_readline() {
   if ! configured_with_readline_dir; then
     local libdir="$(brew --prefix readline 2>/dev/null || true)"
     if [ -d "$libdir" ]; then
-      package_option python configure CPPFLAGS="-I$libdir/include" LDFLAGS="-L$libdir/lib"
+      export CPPFLAGS="-I$libdir/include ${CPPFLAGS}"
+      export LDFLAGS="-L$libdir/lib ${LDFLAGS}"
     else
       return 1
     fi
@@ -1095,7 +1097,8 @@ has_broken_mac_openssl() {
 use_homebrew_openssl() {
   local ssldir="$(brew --prefix openssl 2>/dev/null || true)"
   if [ -d "$ssldir" ]; then
-    package_option python configure CPPFLAGS="-I$ssldir/include" LDFLAGS="-L$ssldir/lib"
+    export CPPFLAGS="-I$ssldir/include ${CPPFLAGS}"
+    export LDFLAGS="-L$ssldir/lib ${LDFLAGS}"
   else
     return 1
   fi
@@ -1109,7 +1112,8 @@ build_package_mac_openssl() {
   OPENSSLDIR="${OPENSSLDIR:-$OPENSSL_PREFIX_PATH/ssl}"
 
   # Tell Python to use this openssl for its extension.
-  package_option python configure CPPFLAGS="-I${OPENSSL_PREFIX_PATH}/include" LDFLAGS="-L${OPENSSL_PREFIX_PATH}/lib"
+  export CPPFLAGS="-I${OPENSSL_PREFIX_PATH}/include ${CPPFLAGS}"
+  export LDFLAGS="-L${OPENSSL_PREFIX_PATH}/lib ${LDFLAGS}"
 
   # Hint OpenSSL that we prefer a 64-bit build.
   export KERNEL_BITS="64"

plugins/python-build/test/build.bats

@@ -125,8 +125,8 @@ OUT
   unstub make
 
   assert_build_log <<OUT
-Python-3.2.1: CPPFLAGS="-I${TMP}/install/include " LDFLAGS="-L${TMP}/install/lib "
-Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib CPPFLAGS=-I$brew_libdir/include LDFLAGS=-L$brew_libdir/lib
+Python-3.2.1: CPPFLAGS="-I$brew_libdir/include -I${TMP}/install/include " LDFLAGS="-L$brew_libdir/lib -L${TMP}/install/lib "
+Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
 make -j 2
 make install
 OUT
@@ -150,8 +150,8 @@ DEF
   unstub make
 
   assert_build_log <<OUT
-Python-3.2.1: CPPFLAGS="-I${TMP}/install/include " LDFLAGS="-L${TMP}/install/lib "
-Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib CPPFLAGS=-I$readline_libdir/include LDFLAGS=-L$readline_libdir/lib
+Python-3.2.1: CPPFLAGS="-I$readline_libdir/include -I${TMP}/install/include " LDFLAGS="-L$readline_libdir/lib -L${TMP}/install/lib "
+Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
 make -j 2
 make install
 OUT