Fix docker runtime compilers versions metadata

Makefile

@@ -69,8 +69,8 @@ endif
 CPU:=		$(shell LC_ALL=en_US.UTF-8 lscpu | grep "Model name" | cut -d":" -f 2 | sort | uniq | awk '{$$1=$$1;print}')
 UCODE:=		$(shell (grep microcode /proc/cpuinfo 2> /dev/null || printf unknown) | sort | uniq | awk '{print $$NF}' || printf unknown)
 KERN:=		$(shell uname -svm)
-CLANGV:=	$(shell (clang -v 2>&1 | head -n 1)) || apk info -a clang | head -n1 | awk '{print $$1}' || printf unknown)
-GCCV:=		$(shell (gcc -v 2>&1 | grep 'gcc version') || apk info -a gcc | head -n1 | awk '{print $$1}' || printf unknown)
+CLANGV:=	$(shell (clang -v 2>&1 | head -n 1)) || (apk info -a clang 2> /dev/null | head -n1 | awk '{print $$1}') || printf unknown)
+GCCV:=		$(shell (gcc -v 2>&1 | grep 'gcc version') || (apk info -a gcc 2> /dev/null | head -n1 | awk '{print $$1}') || printf unknown)
 VULN1:=		$(shell (cat /sys/devices/system/cpu/vulnerabilities/spectre_v1 2> /dev/null || printf unknown))
 VULN2:=		$(shell (cat /sys/devices/system/cpu/vulnerabilities/spectre_v2 2> /dev/null || printf unknown))
 REVISION:=	$(shell git rev-parse --short HEAD)

README.md

@@ -30,7 +30,11 @@ And compilation/linking flags such as:
 - _Fedora 35_
 - _OpenBSD 7.0_ 
 
-A _Dockerfile_ is provided but be wary: the compiled binaries inside the docker image are heavily dependent on the CPU platform/version and _not_ portable. You **have** to build the image on the actual CPU you want to test, otherwise you may stumble upon ```core dumped: illegal instruction``` errors.
+## Docker support 
+
+A _Dockerfile_ is provided and used by ```make docker``` but be wary: the compiled binaries inside the docker image are heavily dependent on the CPU platform/version and _not_ portable.
+
+You **have** to build the image on the actual CPU you want to test, otherwise you may stumble upon ```core dumped: illegal instruction``` errors.
 
 ## Results
 
@@ -38,7 +42,7 @@ Results are stored as JSON objects in an unique file for each run, following thi
 
 ## Dependencies
 
-- Compiler: ```clang``` and ```gcc```
+- Compilers: ```clang``` and ```gcc```
 - Linker: ```lld```
 - For upload: ```openssh``` and ```uuid```
 - The C library static symbols, on Fedora: ```glibc-static```
@@ -49,7 +53,7 @@ Results are stored as JSON objects in an unique file for each run, following thi
 
 ### PoC only 
 
-```make poc``` will compile and execute v1 and v2 executable once using clang and no optimisations.
+```make poc``` will compile and execute v1 and v2 executables once using clang and no optimisations.
 
 ### Within docker
 
@@ -63,9 +67,11 @@ Results are stored as JSON objects in an unique file for each run, following thi
 
 ```make build``` will only build the experiment binaries.
 
-To build using multiple processes:
+### Cleanup
 
-```make [-j XXX] build``` where ```XXX``` is the number of parallel processes.
+```make clean``` will remove experiment binaries and result files.
+
+```make dockerclean``` will remove the _octopus_ image.
 
 ## Results aggregation