fuse_ext2: build with '-std=gnu89'

GCC 6 defaults to '-std=gnu11' for the C language, which has different
semantics for inline functions and triggers build errors.

Fixes #2385

repos/libports/lib/mk/libext2fs.mk

@@ -19,6 +19,8 @@ CC_OPT += -Wno-unused-function -Wno-unused-variable \
           -Wno-unused-but-set-variable -Wno-cpp \
           -Wno-maybe-uninitialized -Wno-uninitialized
 
+CC_C_OPT += -std=gnu89
+
 LIBS += libc
 
 vpath %.c $(EXT2FS_DIR)

repos/libports/src/server/fuse_fs/ext2/target.mk

@@ -17,6 +17,8 @@ CC_OPT += -Wno-unused-function -Wno-unused-variable \
           -Wno-unused-but-set-variable -Wno-cpp \
           -Wno-maybe-uninitialized
 
+CC_C_OPT += -std=gnu89
+
 CC_C_OPT += -Wno-implicit-function-declaration