Comment # 9 on bug 4285 from Vitaly Zaitsev

> Try removing the brackets from them

cc: error: RPM_OPT_FLAGS: No such file or directory

GYP doc:
https://chromium.googlesource.com/external/gyp/+/md-pages/docs/InputFormatReference.md#Command-Expansions

Trying also such:

'<!@(echo $CFLAGS)',

got another error:

Error evaluating generator expression: $<BOOL:-pipe -g -Wall -W -fPIC
-Wno-unused-result -Wno-unused-variable -Wno-unused-parameter
-Wno-unused-function -Wno-switch -Wno-comment -Wno-unused-but-set-variable
-Wno-missing-field-initializers -O2 -g -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong
--param=ssp-buffer-size=4 -grecord-gcc-switches
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic -pipe -g
-Wall -W -fPIC -Wno-unused-result -Wno-unused-variable -Wno-unused-parameter
-Wno-unused-function -Wno-switch -Wno-comment -Wno-unused-but-set-variable
-Wno-missing-field-initializers -std=gnu++1y -pthread
-I/usr/include/libappindicator-0.1 -I/usr/include/libdbusmenu-glib-0.4
-I/usr/include/gtk-2.0 -I/usr/lib64/gtk-2.0/include -I/usr/include/pango-1.0
-I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1
-I/usr/include/libdrm -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libpng16
-I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0
-I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/freetype2
-I/usr/include/libpng16 -I/usr/include/freetype2 -I/usr/include/libpng16
-pthread -I/usr/include/gtk-2.0 -I/usr/lib64/gtk-2.0/include
-I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo
-I/usr/include/pixman-1 -I/usr/include/libdrm -I/usr/include/gdk-pixbuf-2.0
-I/usr/include/libpng16 -I/usr/include/pango-1.0 -I/usr/include/harfbuzz
-I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include
-I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/freetype2
-I/usr/include/libpng16 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include
-pthread -I/usr/include/dee-1.0 -I/usr/include/gio-unix-2.0/
-I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -O2 -g -pipe -Wall
-Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic