hdl/**/Makefile: enable early rules termination (#513)

- set default shell to bash
- add pipefail option

Fixes #412

hdl/mixed/blink/Makefile

@@ -18,6 +18,9 @@ YOSYS      ?= yosys
 NEXTPNR    ?= nextpnr-ice40
 ICEPACK    ?= icepack
 
+SHELL = /bin/bash
+.SHELLFLAGS = -o pipefail -c
+
 QUIET = @
 
 # If ghdl-yosys-plugin is built as a module (not the case with fomu-toolchain)

hdl/verilog/blink-expanded/Makefile

@@ -9,6 +9,9 @@ YOSYS     ?= yosys
 NEXTPNR   ?= nextpnr-ice40
 ICEPACK   ?= icepack
 
+SHELL = /bin/bash
+.SHELLFLAGS = -o pipefail -c
+
 QUIET = @
 
 # If a container engine is used, each tool is executed in a separated container

hdl/verilog/blink/Makefile

@@ -9,6 +9,9 @@ YOSYS     ?= yosys
 NEXTPNR   ?= nextpnr-ice40
 ICEPACK   ?= icepack
 
+SHELL = /bin/bash
+.SHELLFLAGS = -o pipefail -c
+
 QUIET = @
 
 # If a container engine is used, each tool is executed in a separated container

hdl/vhdl/blink/Makefile

@@ -12,6 +12,9 @@ YOSYS      ?= yosys
 NEXTPNR    ?= nextpnr-ice40
 ICEPACK    ?= icepack
 
+SHELL = /bin/bash
+.SHELLFLAGS = -o pipefail -c
+
 QUIET = @
 
 # If ghdl-yosys-plugin is built as a module (not the case with fomu-toolchain)