--- old/make/autoconf/flags-cflags.m4	2018-12-12 21:42:46.668084092 +0100
+++ new/make/autoconf/flags-cflags.m4	2018-12-12 21:42:46.292084095 +0100
@@ -559,7 +559,7 @@
     TOOLCHAIN_CFLAGS="-errshort=tags"
 
     TOOLCHAIN_CFLAGS_JDK="-mt $TOOLCHAIN_FLAGS"
-    TOOLCHAIN_CFLAGS_JDK_CONLY="-xc99=%none -xCC -Xa -W0,-noglobal $TOOLCHAIN_CFLAGS" # C only
+    TOOLCHAIN_CFLAGS_JDK_CONLY="-std=c99 -xCC -W0,-noglobal $TOOLCHAIN_CFLAGS" # C only
     TOOLCHAIN_CFLAGS_JDK_CXXONLY="-features=no%except -norunpath -xnolib" # CXX only
     TOOLCHAIN_CFLAGS_JVM="-template=no%extdef -features=no%split_init \
         -library=stlport4 -mt -features=no%except $TOOLCHAIN_FLAGS"