update README.en.md.

add Building methods

README.en.md

@@ -7,3 +7,23 @@
 - other standard functions in C11 Annex K will be analyzed in the future and implemented in this organization if necessary.
 
 - handles the release, update, and maintenance of bounds_checking_function.
+
+#### Building methods
+
+-compilation steps
+
+1. Add all the .c files under /src to the source code listing for the build script.
+
+2. In the build options, specify the header directory and the build options required for the project (for example, add  
+-Ipath_to_include -fstack-protector-strong -fPIC -Wall -D_FORTIFY_SOURCE=2 -O2 in CFLAGS).
+
+3. Generate .o files for each .c file.
+
+4. Generate static or shared libraries for .o files according to project requirements.
+
+-compiling examples:
+```
+gcc -o memcpy_s.o -c -Iinclude -fstack-protector-strong -fPIC -Wall -D_FORTIFY_SOURCE=2 -O2 src/memcpy_s.c
+```
+
+