Sets -Wno-error=address-of-packed-member built with GCC9

See also frugalos#10.

install_deps.sh

@@ -41,6 +41,15 @@ cd liberasurecode/
 git checkout 1.5.0
 ./autogen.sh
 CFLAGS="-I${BUILD_DIR}/jerasure/include -I${BUILD_DIR}/include"
+# Since gcc9, gcc reports warnings about taking the address of a packed member.
+# jerasure uses autoconf and autoconf looks for gcc and cc at first if CC is not set in the environment.
+# See https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/C-Compiler.html for more details.
+if type gcc > /dev/null 2>&1; then
+    GCC_MAJOR_VERSION=$(gcc -dumpversion | cut -f 1 -d '.')
+    if [ $GCC_MAJOR_VERSION -ge 9 ]; then
+        CFLAGS="$CFLAGS -Wno-error=address-of-packed-member"
+    fi
+fi
 if [ "$(uname)" == "Darwin" ]; then
     CFLAGS="$CFLAGS -Wno-error=address-of-packed-member"
 fi