llvm-config: add page (#6498)

pages/common/llvm-config.md

@@ -0,0 +1,17 @@
+# llvm-config
+
+> Get various configuration information needed to compile programs which use LLVM.
+> Typically called from build systems, like in Makefiles or configure scripts.
+> More information: <https://llvm.org/docs/CommandGuide/llvm-config.html>.
+
+- Compile and link an LLVM based program:
+
+`clang++ $(llvm-config --cxxflags --ldflags --libs) --output {{path/to/output_executable}} {{path/to/source.cc}}`
+
+- Print the `PREFIX` of your LLVM installation:
+
+`llvm-config --prefix`
+
+- Print all targets supported by your LLVM build:
+
+`llvm-config --targets-built`