Get rid of pkg-config + new package definitions

For mirage/mirage#969
Along with:
mirage-platform: 0612bdbfe1eeb004ad923991178256feb780d14c
ocaml-freestanding: c5bf86ce29872b65a12ac42b9104f15f063d644e

Instead of using pkg-config, cflags and libs are fetched from files in
the library folder.

.gitignore

@@ -4,3 +4,4 @@ setup.data
 setup.log
 .*.swp
 /*.install
+.merlin

lib_impl/freestanding/dune

@@ -4,11 +4,13 @@
   (libraries   lwt cstruct mirage-solo5 ocaml-freestanding)
   (implements mirage-entropy)
   (c_names     entropy_cpu_stubs)
-  (c_flags     (:include cflags.sexp) -O3 -std=c99 -Wall -Wpedantic
+  (c_flags     (:include cflags.sexp) (:include custom_flags) -O3 -std=c99 -Wall -Wpedantic
   )
 )
 
 (rule (copy# ../entropy_cpu_stubs.c entropy_cpu_stubs.c))
 (rule (copy# ../entropy.ml entropy.ml))
 
-(rule (with-stdout-to cflags.sexp (run ./cflags.sh)))
+(rule (with-stdout-to cflags.sexp (run ../cflags.sh)))
+
+(rule (copy %{lib:ocaml-freestanding:cflags} custom_flags))

lib_impl/unix/dune

@@ -5,10 +5,10 @@
   (implements  mirage-entropy)
   (c_names     entropy_cpu_stubs)
   (c_flags     (:include cflags.sexp) -O3 -std=c99 -Wall -Wpedantic
-  ) 
+  )
 )
 
 (rule (copy# ../entropy_cpu_stubs.c entropy_cpu_stubs.c))
 (rule (copy# ../entropy.ml entropy.ml))
 
-(rule (with-stdout-to cflags.sexp (run ./cflags.sh)))
+(rule (with-stdout-to cflags.sexp (run ../cflags.sh)))

lib_impl/xen/dune

@@ -4,11 +4,13 @@
   (libraries   lwt cstruct mirage-xen)
   (implements mirage-entropy)
   (c_names     entropy_cpu_stubs)
-  (c_flags     (:include cflags.sexp) -O3 -std=c99 -Wall -Wpedantic
-  ) 
+  (c_flags     (:include cflags.sexp) (:include custom_flags) -O3 -std=c99 -Wall -Wpedantic
+  )
 )
 
 (rule (copy# ../entropy_cpu_stubs.c entropy_cpu_stubs.c))
 (rule (copy# ../entropy.ml entropy.ml))
 
-(rule (with-stdout-to cflags.sexp (run ./cflags.sh)))
+(rule (with-stdout-to cflags.sexp (run ../cflags.sh)))
+
+(rule (copy %{lib:mirage-xen-posix:posix-cflags} custom_flags))

mirage-entropy-freestanding.opam

@@ -10,22 +10,19 @@ license:      "BSD2"
 
 build: [ "dune" "build" "-p" "mirage-entropy-freestanding"]
 depends: [
-  "dune" {build}
+  "dune" {build & >= "1.7"}
   "ocaml" {>= "4.04.2"}
-  "cstruct"
+  "cstruct" {>= "1.4.0"}
   "ocaml-freestanding"
   "mirage-entropy"
   "mirage-solo5"
   "lwt"
 ]
-conflicts: [
-  "cstruct" {<"1.4.0"}
-]
 tags: [ "org:mirage"]
 available: [
   arch = "arm" | arch = "x86_32" | arch = "x86_64" | arch = "arm64"
 ]
-synopsis: "Entropy source for MirageOS unikernels"
+synopsis: "Mirage entropy implementation for freestanding"
 description: """
 mirage-entropy implements various entropy sources for MirageOS unikernels:
 - timer based ones (see [whirlwind RNG paper](https://www.ieee-security.org/TC/SP2014/papers/Not-So-RandomNumbersinVirtualizedLinuxandtheWhirlwindRNG.pdf))

mirage-entropy-unix.opam

@@ -10,21 +10,18 @@ license:      "BSD2"
 
 build: [ "dune" "build" "-p" "mirage-entropy-unix"]
 depends: [
-  "dune" {build}
+  "dune" {build & >= "1.7"}
   "ocaml" {>= "4.04.2"}
-  "cstruct"
+  "cstruct" {>= "1.4.0"}
   "lwt"
   "mirage-entropy"
   "mirage-unix"
 ]
-conflicts: [
-  "cstruct" {<"1.4.0"}
-]
 tags: [ "org:mirage"]
 available: [
   arch = "arm" | arch = "x86_32" | arch = "x86_64" | arch = "arm64"
 ]
-synopsis: "Entropy source for MirageOS unikernels"
+synopsis: "Mirage entropy implementation for Unix"
 description: """
 mirage-entropy implements various entropy sources for MirageOS unikernels:
 - timer based ones (see [whirlwind RNG paper](https://www.ieee-security.org/TC/SP2014/papers/Not-So-RandomNumbersinVirtualizedLinuxandtheWhirlwindRNG.pdf))

mirage-entropy-xen.opam

@@ -10,22 +10,18 @@ license:      "BSD2"
 
 build: [ "dune" "build" "-p" "mirage-entropy-xen"]
 depends: [
-  "dune" {build}
+  "dune" {build & >= "1.7"}
   "ocaml" {>= "4.04.2"}
-  "cstruct"
-  "mirage-xen"
+  "cstruct" {>= "1.4.0"}
+  "mirage-xen" {>= "2.2.0"}
   "mirage-entropy"
   "lwt"
 ]
-conflicts: [
-  "cstruct" {<"1.4.0"}
-  "mirage-xen" {<"2.2.0"}
-]
 tags: [ "org:mirage"]
 available: [
   arch = "arm" | arch = "x86_32" | arch = "x86_64" | arch = "arm64"
 ]
-synopsis: "Entropy source for MirageOS unikernels"
+synopsis: "Mirage entropy implementation for Xen"
 description: """
 mirage-entropy implements various entropy sources for MirageOS unikernels:
 - timer based ones (see [whirlwind RNG paper](https://www.ieee-security.org/TC/SP2014/papers/Not-So-RandomNumbersinVirtualizedLinuxandtheWhirlwindRNG.pdf))

mirage-entropy.opam

@@ -10,14 +10,11 @@ license:      "BSD2"
 
 build: [ "dune" "build" "-p" "mirage-entropy"]
 depends: [
-  "dune" {build}
+  "dune" {build & >= "1.7"}
   "ocaml" {>= "4.04.2"}
-  "cstruct"
+  "cstruct" {>="1.4.0"}
   "lwt"
 ]
-conflicts: [
-  "cstruct" {<"1.4.0"}
-]
 tags: [ "org:mirage"]
 available: [
   arch = "arm" | arch = "x86_32" | arch = "x86_64" | arch = "arm64"