Add descriptive header to build scripts.

build.sh

@@ -1,4 +1,10 @@
 #!/usr/bin/env bash
+#
+# Build and install the cctools the SDK and macports.
+#
+# This script requires the OS X SDK and the Clang/LLVM compiler.
+#
+
 
 pushd "${0%/*}" &>/dev/null
 

build_binutils.sh

@@ -1,4 +1,11 @@
 #!/usr/bin/env bash
+#
+# Build and install the GNU binutils and the GNU Debugger (gdb) for
+# target OS X.
+#
+# You may want to run this script if you want to build software using
+# gcc. Please refer to the README.md for details.
+#
 
 pushd "${0%/*}" &>/dev/null
 

build_clang.sh

@@ -1,4 +1,11 @@
 #!/usr/bin/env bash
+#
+# Build and install Clang/LLVM, using `gcc`.
+#
+# You only need to run this if your distribution does not provide
+# clang - or if you want to build your own version from a recent
+# source tree.
+#
 
 pushd "${0%/*}" &>/dev/null
 

build_compiler_rt.sh

@@ -1,4 +1,10 @@
 #!/usr/bin/env bash
+#
+# Build and install the "compiler-rt" runtime library.
+#
+# This requires that you already finished `build.sh`.
+# Please refer to README.COMPILER-RT.md for details.
+#
 
 pushd "${0%/*}" &>/dev/null
 

build_gcc.sh

@@ -1,4 +1,11 @@
 #!/usr/bin/env bash
+#
+# Build and install gcc/gcc++ as a cross-compiler with target OSX,
+# using `clang`.
+#
+# You may want to run this script if you want to build software using
+# gcc. Please refer to the README.md for details.
+#
 
 pushd "${0%/*}" &>/dev/null
 

build_llvm_dsymutil.sh

@@ -1,4 +1,9 @@
 #!/usr/bin/env bash
+#
+# Build and install the `llvm-dsymutil` tool required for debugging.
+#
+# Please refer to README.DEBUGGING.md for details.
+#
 
 pushd "${0%/*}" &>/dev/null