Add compiler option examples

cmake/sample_defs/arch_build.cmake

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+#
+# Example arch_build.cmake
+# -------------------------
+#
+# This file will be automatically included in the arch-specific build scope
+#
+# Definitions and options specified here will be used when cross-compiling 
+# _all_ FSW code for _all_ targets defined in targets.cmake.
+#
+# Avoid machine-specific code generation options in this file (e.g. -f,-m options); such 
+# options should be localized to the toolchain file such that they will only be
+# included on the machines where they apply.
+# 
+# CAUTION: In heterogeneous environments where different cross compilers are
+# used for different CPUs, particularly if from different vendors, it is likely
+# that compile options will need to be different as well.
+#
+# In general, options in this file can only be used in cases where all CPUs use a
+# compiler from the same vendor and/or are all GCC based such that they accept similar 
+# command line options.
+#
+# This file can alternatively be named as "arch_build_${TARGETSYSTEM}.cmake" 
+# where ${TARGETSYSTEM} represents the system type, matching the toolchain.
+#
+# These example options assume a GCC-style toolchain is used for cross compilation,
+# and uses the same warning options that are applied at the mission level. 
+#
+add_compile_options(
+    -std=c99                # Target the C99 standard (without gcc extensions) 
+    -pedantic               # Issue all the warnings demanded by strict ISO C
+    -Wall                   # Warn about most questionable operations
+    -Wstrict-prototypes     # Warn about missing prototypes
+    -Wwrite-strings         # Warn if not treating string literals as "const"
+    -Wpointer-arith         # Warn about suspicious pointer operations
+    -Werror                 # Treat warnings as errors (code should be clean) 
+)
+

cmake/sample_defs/mission_build.cmake

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+#
+# Example mission_build.cmake
+# ---------------------------
+#
+# This file will be automatically included in the top level ("mission") build scope
+#
+# Definitions and options specified here will be used when building local tools and
+# other code that runs on the development host, but do _NOT_ apply to flight software
+# (embedded) code or anything built for the target machine. 
+#
+# These options assume a GCC toolchain but a similar set should be applicable to clang.
+#
+add_compile_options(
+    -std=c99                # Target the C99 standard (without gcc extensions) 
+    -pedantic               # Issue all the warnings demanded by strict ISO C
+    -Wall                   # Warn about most questionable operations
+    -Wstrict-prototypes     # Warn about missing prototypes
+    -Wwrite-strings         # Warn if not treating string literals as "const"
+    -Wpointer-arith         # Warn about suspicious pointer operations
+    -Werror                 # Treat warnings as errors (code should be clean) 
+)
+
+# The _XOPEN_SOURCE directive is required for glibc to enable conformance with the
+# the X/Open standard version 6, which includes POSIX.1c as well as SUSv2/UNIX98 extensions.
+add_definitions(
+    -D_XOPEN_SOURCE=600
+)